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1 .\" Copyright (c) 2008 by Rhyolite Software, LLC |
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2 .\" |
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3 .\" This agreement is not applicable to any entity which sells anti-spam |
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4 .\" solutions to others or provides an anti-spam solution as part of a |
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5 .\" security solution sold to other entities, or to a private network |
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6 .\" which employs the DCC or uses data provided by operation of the DCC |
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7 .\" but does not provide corresponding data to other users. |
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8 .\" |
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9 .\" Permission to use, copy, modify, and distribute this software without |
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10 .\" changes for any purpose with or without fee is hereby granted, provided |
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11 .\" that the above copyright notice and this permission notice appear in all |
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12 .\" copies and any distributed versions or copies are either unchanged |
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13 .\" or not called anything similar to "DCC" or "Distributed Checksum |
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14 .\" Clearinghouse". |
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15 .\" |
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16 .\" Parties not eligible to receive a license under this agreement can |
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17 .\" obtain a commercial license to use DCC by contacting Rhyolite Software |
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18 .\" at sales@rhyolite.com. |
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19 .\" |
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20 .\" A commercial license would be for Distributed Checksum and Reputation |
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21 .\" Clearinghouse software. That software includes additional features. This |
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22 .\" free license for Distributed ChecksumClearinghouse Software does not in any |
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23 .\" way grant permision to use Distributed Checksum and Reputation Clearinghouse |
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24 .\" software |
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25 .\" |
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26 .\" THE SOFTWARE IS PROVIDED "AS IS" AND RHYOLITE SOFTWARE, LLC DISCLAIMS ALL |
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27 .\" WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES |
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28 .\" OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL RHYOLITE SOFTWARE, LLC |
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29 .\" BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES |
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30 .\" OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, |
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31 .\" WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, |
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32 .\" ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS |
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33 .\" SOFTWARE. |
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34 .\" |
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35 .\" Rhyolite Software DCC 1.3.103-1.168 $Revision$ |
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36 .\" |
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37 .Dd February 26, 2009 |
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38 .ds volume-ds-DCC Distributed Checksum Clearinghouse |
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39 .Dt dccm 8 DCC |
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40 .Os " " |
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41 .Sh NAME |
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42 .Nm dccm |
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43 .Nd Distributed Checksum Clearinghouse Milter Interface |
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44 .Sh SYNOPSIS |
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45 .Bk -words |
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46 .Nm |
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47 .Op Fl VdbxANQ |
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48 .Op Fl G Ar on | off | noIP | IPmask/xx |
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49 .Op Fl h Ar homedir |
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50 .Op Fl I Ar user |
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51 .br |
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52 .Op Fl p Ar protocol:filename | protocol:port@host |
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53 .Op Fl m Ar map |
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54 .br |
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55 .Op Fl w Ar whiteclnt |
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56 .Op Fl U Ar userdirs |
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57 .Op Fl a Ar IGNORE | REJECT | DISCARD |
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58 .br |
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59 .Oo |
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60 .Fl t Xo |
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61 .Sm off |
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62 .Ar type, |
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63 .Op Ar log-thold, |
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64 .Ar rej-thold |
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65 .Sm on |
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66 .Xc |
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67 .Oc |
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68 .Oo |
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69 .Fl g Xo |
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70 .Sm off |
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71 .Op Ar not- |
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72 .Ar type |
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73 .Sm on |
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74 .Xc |
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75 .Oc |
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76 .Op Fl S Ar header |
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77 .br |
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78 .Op Fl l Ar logdir |
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79 .Op Fl R Ar rundir |
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80 .Op Fl r Ar rejection-msg |
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81 .Op Fl j Ar maxjobs |
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82 .Op Fl B Ar dnsbl-option |
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83 .Op Fl L Ar ltype,facility.level |
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84 .Ek |
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85 .Sh DESCRIPTION |
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86 .Nm |
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87 is a daemon built with the sendmail milter interface intended to connect |
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88 .Xr sendmail 8 |
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89 to DCC servers. |
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90 When built with the milter filter machinery and configured to talk to |
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91 .Nm |
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92 in the |
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93 .Pa sendmail.cf |
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94 file, |
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95 sendmail passes all email to |
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96 .Nm |
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97 which in turn reports related checksums to the nearest DCC server. |
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98 .Nm |
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99 then adds an |
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100 .Em X-DCC |
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101 SMTP header line to the message. |
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102 Sendmail is told to reject the message if it is unsolicited bulk mail. |
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103 .Pp |
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104 .Nm Dccm |
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105 sends reports of checksums related to mail received by DCC clients |
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106 and queries about the total number of reports of particular checksums. |
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107 A DCC server receives |
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108 .Em no |
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109 mail, address, headers, or other information, |
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110 but only cryptographically secure checksums of such information. |
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111 A DCC server cannot determine the text or other information that corresponds |
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112 to the checksums it receives. |
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113 Its only acts as a clearinghouse of counts for checksums computed by clients. |
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114 For complete privacy as far as the DCC is concerned, |
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115 the checksums of purely internal mail or other |
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116 mail that is known to not be unsolicited bulk can be listed in a whitelist |
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117 to not be reported to the DCC server. |
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118 .Pp |
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119 Since the checksums of messages that are whitelisted locally |
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120 by the |
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121 .Fl w Ar whiteclnt |
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122 file are not reported to the DCC server, |
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123 .Nm |
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124 knows nothing about the total recipient counts for their checksums and |
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125 so cannot add |
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126 .Em X-DCC |
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127 header lines to such messages. |
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128 Sendmail does not tell |
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129 .Nm |
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130 about messages that are not received by sendmail via SMTP, including messages |
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131 submitted locally and received via UUCP, and so they also do not receive |
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132 .Em X-DCC |
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133 header lines. |
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134 .Pp |
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135 Enable the daemon and put its parameters in the |
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136 .Pa dcc_conf |
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137 file and start the daemon with the |
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138 .Pa @libexecdir@/start-dccm |
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139 or |
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140 .Pa var/dcc/libexec/rcDCC |
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141 script. |
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142 .Pp |
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143 The list of servers that |
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144 .Nm |
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145 contacts is in the memory mapped file |
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146 .Pa map |
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147 shared by local DCC clients. |
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148 The file is maintained with |
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149 .Xr cdcc 8 . |
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150 .Ss OPTIONS |
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151 The following options are available: |
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152 .Bl -tag -width 3n |
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153 .It Fl V |
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154 displays the version of |
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155 .Nm . |
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156 .It Fl d |
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157 enables debugging output from the DCC client software. |
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158 Additional |
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159 .Fl d |
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160 options increase the number of messages. |
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161 A single |
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162 .Fl d |
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163 aborted SMTP transactions including those from some "dictionary attacks." |
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164 .It Fl b |
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165 causes the daemon to not detach itself from the controlling tty |
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166 and put itself into the background. |
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167 .It Fl x |
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168 causes the daemon to try "extra hard" to contact a DCC server. |
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169 Since it is usually more important to deliver mail than to report its |
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170 checksums, |
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171 .Nm |
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172 normally does not delay too long while trying to contact a DCC server. |
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173 It will not try again for several seconds after a failure. |
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174 With |
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175 .Fl x , |
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176 it will always try to contact the DCC server |
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177 and it will tell the MTA to answer the DATA command with a 4yz |
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178 temporary failure. |
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179 .It Fl A |
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180 adds to existing X-DCC headers in the message |
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181 instead of replacing existing headers |
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182 of the brand of the current server. |
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183 .It Fl N |
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184 neither adds, deletes, nor replaces existing X-DCC headers in the message. |
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185 Each message is logged, rejected, and otherwise handled the same. |
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186 .It Fl Q |
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187 only queries the DCC server about the checksums of messages |
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188 instead of reporting and querying. |
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189 This is useful when |
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190 .Nm |
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191 is used to filter mail that has already been reported to a DCC |
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192 server by another DCC client. |
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193 No single mail message should be reported to a DCC |
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194 server more than once per recipient, |
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195 because each report will increase the apparent "bulkness" of the message. |
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196 .Pp |
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197 It is better to use |
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198 .Em MXDCC |
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199 lines in the global |
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200 .Pa whiteclnt |
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201 file for your MX mail servers that use DCC than |
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202 .Fl Q . |
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203 .It Fl G Ar on | off | noIP | IPmask/xx |
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204 controls |
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205 .Em greylisting . |
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206 At least one working greylist server must be listed in the |
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207 .Pa map |
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208 file in the DCC home directory. |
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209 If more than one is named, |
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210 they must "flood" or change checksums and they must use the |
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211 same |
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212 .Fl G |
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213 parameters. |
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214 See |
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215 .Xr dccd 8 . |
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216 Usually all dccm or dccifd DCC client processes use the same |
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217 .Fl G |
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218 parameters. |
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219 .Pp |
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220 .Ar IPmask/xx |
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221 and |
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222 .Ar noIP |
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223 remove part or all of the IP address from the greylist triple. |
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224 The CIDR block size, |
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225 .Ar xx , |
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226 must be between 1 and 128. |
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227 96 is added to block sizes smaller than 33 to make them appropriate for |
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228 the IPv6 addresses used by the DCC. |
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229 .Ar IPmask/96 |
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230 differs from |
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231 .Ar noIP |
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232 for IPv4 addresses, |
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233 because the former retains the IPv4 to IPv6 mapping prefix. |
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234 .It Fl h Ar homedir |
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235 overrides the default DCC home directory, |
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236 .Pa @prefix@ . |
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237 .It Fl I Ar user |
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238 specifies the UID and GID of the process. |
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239 .It Fl p Ar protocol:filename | protocol:port@host |
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240 specifies the protocol and address by which sendmail will contact |
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241 .Nm dccm . |
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242 The default is a UNIX domain socket in the "run" directory, |
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243 .Pa @dcc_rundir@/dccm . |
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244 (See also |
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245 .Fl R) |
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246 This protocol and address must match the value in |
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247 .Pa sendmail.cf . |
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248 This mechanism can be used to connect |
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249 .Nm |
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250 on one computer to sendmail on another computer |
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251 when a port and host name or IP address are used. |
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252 .It Fl m Ar map |
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253 specifies a name or path of the memory mapped parameter file instead |
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254 of the default |
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255 .Pa map |
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256 file in the DCC home directory. |
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257 It should be created with the |
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258 .Xr cdcc 8 |
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259 command. |
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260 .It Fl w Ar whiteclnt |
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261 specifies an optional file containing filtering parameters |
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262 as well as SMTP client IP addresses, |
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263 SMTP envelope values, and header values |
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264 of mail that is spam or is not spam and does not need a |
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265 .Em X-DCC |
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266 header, |
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267 and whose checksums should not be reported to the DCC server. |
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268 .Pp |
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269 If the pathname |
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270 .Ar whiteclnt |
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271 is not absolute, it is relative to the DCC home directory. |
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272 .Pp |
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273 The format of the |
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274 .Nm |
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275 whiteclnt file is the same as the |
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276 .Pa whitelist |
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277 files used by |
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278 .Xr dbclean 8 |
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279 and the |
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280 .Pa whiteclnt |
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281 file used by |
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282 .Xr dccproc 8 . |
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283 See |
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284 .Xr dcc 8 |
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285 for a description of DCC white and blacklists. |
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286 Because the contents of the |
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287 .Ar whiteclnt |
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288 file are used frequently, a companion file is automatically |
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289 created and maintained. |
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290 It has the same pathname but with an added suffix of |
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291 .Ar .dccw |
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292 and contains a memory mapped hash table of the main file. |
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293 .Pp |
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294 A whitelist entry ("OK") or two or more semi-whitelistings ("OK2") |
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295 for one of the message's checksums prevents all of |
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296 the message's checksums from being reported to the DCC server |
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297 and the addition of a |
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298 .Em X-DCC |
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299 header line by |
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300 .Nm |
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301 A whitelist entry for a checksum |
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302 also prevents rejecting or discarding the message based on DCC recipient |
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303 counts as specified by |
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304 .Fl a |
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305 and |
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306 .Fl t . |
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307 Otherwise, one or more checksums with blacklisting entries ("MANY") cause |
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308 all of the message's |
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309 checksums to be reported to the server with an addressee count of "MANY". |
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310 .Pp |
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311 If the message has a single recipient, an |
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312 .Ar env_To |
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313 .Ar whiteclnt |
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314 entry of "OK" for the checksum of its recipient address acts like any other |
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315 .Ar whiteclnt |
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316 entry of "OK." |
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317 When the SMTP message has more than one recipient, |
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318 the effects can be complicated. |
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319 When a message has several recipients with some but not all listed in the |
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320 .Ar whiteclnt |
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321 file, |
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322 .Nm |
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323 tries comply with the wishes of the users who want filtering as |
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324 well as those who don't by silently not delivering the message to |
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325 those who want filtering (i.e. are not whitelisted) and delivering |
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326 the message to don't want filtering. |
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327 .It Fl U Ar userdirs |
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328 enables per-user |
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329 .Pa whiteclnt |
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330 files and log directories. |
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331 Each target of a message can have a directory of log files named |
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332 .Ar usedirs/${dcc_userdir}/log |
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333 where |
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334 .Em ${dcc_userdir} |
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335 is the |
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336 .Pa sendmail.cf |
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337 macro described below. |
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338 If |
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339 .Em ${dcc_userdir} |
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340 is not set, |
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341 .Ar userdirs/${rcpt_mailer}/${rcpt_addr}/log |
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342 is used. |
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343 The most likely value of |
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344 .Ar mailer |
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345 is |
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346 .Ar local . |
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347 Appropriate values for both |
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348 .Ar ${rcpt_mailer} |
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349 and |
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350 .Ar ${rcpt_addr} |
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351 can be seen by examining |
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352 .Em env_To |
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353 lines in |
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354 .Fl l Ar logdir |
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355 files. |
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356 If it is not absolute, |
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357 .Ar userdirs |
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358 is relative to the DCC home directory. |
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359 The directory containing the log files must be named |
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360 .Ar log |
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361 and it must be writable by the |
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362 .Nm |
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363 process. |
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364 Each log directory must exist or logging for the corresponding |
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365 is silently disabled. |
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366 The files created in the log directory are owned by the UID of the |
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367 .Nm |
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368 process, |
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369 but they have |
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370 .Em group |
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371 and |
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372 .Em other |
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373 read and write permissions copied from the corresponding |
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374 .Ar log |
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375 directory. |
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376 To ensure the privacy of mail, |
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377 it may be good to make the directories readable only by |
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378 .Em owner |
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379 and |
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380 .Em group , |
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381 and to use a |
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382 .Xr cron |
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383 script that changes the owner of each file to match the grandparent |
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384 .Ar addr |
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385 directory. |
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386 .Pp |
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387 There can also be a per -user whitelist file named |
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388 .Ar userdirs/${dcc_userdir}/whiteclnt |
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389 or if |
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390 .Ar ${dcc_userdir} |
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391 is not set, |
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392 .Ar userdirs/${rcpt_mailer}/${rcpt_addr} |
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393 per-user whitelist files. |
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394 Any checksum that is not white- or blacklisted by an individual |
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395 addressee's |
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396 .Pa whiteclnt |
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397 file is checked in the main |
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398 .Fl w whiteclnt |
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399 file. |
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400 A missing per-addressee |
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401 .Ar whiteclnt |
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402 file is the same as an empty file. |
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403 Relative paths for files included in per-addressee files |
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404 are resolved in the DCC home directory. |
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405 The |
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406 .Ar whiteclnt |
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407 files and the |
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408 .Ar addr |
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409 directories containing them must be writable by the |
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410 .Nm |
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411 process. |
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412 .Pp |
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413 .Ar Option |
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414 lines in per-user whiteclnt files can be used to modify many aspects of |
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415 .Nm |
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416 filtering, |
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417 as described in the main |
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418 .Xr dcc |
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419 man page. |
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420 For example, an |
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421 .Ar option dcc-off |
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422 line turns off DCC filtering for individual mailboxes. |
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423 .It Fl a Ar IGNORE | REJECT | DISCARD |
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424 specifies the action taken when |
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425 DCC server counts or |
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426 .Fl t |
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427 thresholds say that a message is unsolicited and bulk. |
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428 .Ar IGNORE |
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429 causes the message to be unaffected except for adding the |
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430 .Em X-DCC |
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431 header line to the message. |
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432 This turns off DCC filtering. |
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433 .Pp |
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434 Spam can also be |
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435 .Ar REJECT Ns ed |
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436 or accepted and silently |
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437 .Ar DISCARD Ns ed |
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438 without being delivered to local mailboxes. |
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439 The default is |
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440 .Ar REJECT . |
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441 .Pp |
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442 Mail forwarded via IP addresses marked |
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443 .Em MX |
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444 or |
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445 .Em MXDCC |
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446 in the main |
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447 .Pa whiteclnt |
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448 file is treated |
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449 as if |
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450 .Fl a Ar DISCARD |
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451 were specified. |
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452 This prevents "bouncing" spam. |
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453 .Pp |
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454 Determinations that mail is or is not spam from sendmail via |
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455 .Em ${dcc_isspam} |
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456 or |
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457 .Em ${dcc_notspam} |
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458 macros override |
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459 .Fl a . |
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460 The effects of the |
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461 .Fl w Ar whiteclnt |
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462 are not affected by |
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463 .Fl a . |
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464 .It Fl t Xo |
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465 .Sm off |
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466 .Ar type, |
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467 .Op Ar log-thold, |
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468 .Ar rej-thold |
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469 .Sm on |
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470 .Xc |
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471 sets logging and "spam" thresholds for checksum |
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472 .Ar type . |
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473 The checksum types are |
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474 .Ar IP , |
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475 .Ar env_From , |
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476 .Ar From , |
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477 .Ar Message-ID , |
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478 .Ar substitute , |
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479 .Ar Received , |
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480 .Ar Body , |
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481 .Ar Fuz1 , |
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482 .Ar Fuz2 , |
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483 .Ar rep-total , |
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484 and |
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485 .Ar rep . |
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486 The first six, |
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487 .Ar IP |
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488 through |
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489 .Ar substitute , |
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490 have no effect except when a local DCC server configured with |
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491 .Fl K |
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492 is used. |
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493 The |
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494 .Ar substitute |
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495 thresholds apply to the first substitute heading encountered in the mail |
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496 message. |
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497 The string |
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498 .Ar ALL |
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499 sets thresholds for all types, but is unlikely to be useful except for |
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500 setting logging thresholds. |
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501 The string |
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502 .Ar CMN |
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503 specifies the commonly used checksums |
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504 .Ar Body , |
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505 .Ar Fuz1 , |
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506 and |
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507 .Ar Fuz2 . |
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508 .Ar Rej-thold |
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509 and |
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510 .Ar log-thold |
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511 must be numbers, the string |
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512 .Ar NEVER , |
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513 or the string |
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514 .Ar MANY |
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515 indicating millions of targets. |
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516 Counts from the DCC server as large as the threshold for any single type |
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517 are taken as sufficient evidence |
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518 that the message should be logged or rejected. |
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519 .Pp |
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520 .Ar Log-thold |
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521 is the threshold at which messages are logged. |
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522 It can be handy to log messages at a lower threshold to find |
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523 solicited bulk mail sources such as mailing lists. |
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524 If no logging threshold is set, |
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525 only rejected mail and messages with complicated combinations of white |
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526 and blacklisting are logged. |
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527 Messages that reach at least one of their rejection thresholds are |
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528 logged regardless of logging thresholds. |
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529 .Pp |
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530 .Ar Rej-thold |
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531 is the threshold at which messages are considered "bulk," |
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532 and so should be rejected or discarded if not whitelisted. |
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533 .Pp |
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534 DCC Reputation thresholds in the commercial version |
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535 of the DCC are controlled by thresholds on checksum types |
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536 .Ar rep |
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537 and |
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538 .Ar rep-total . |
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539 Messages from an IP address that the DCC database says has sent |
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540 more than |
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541 .Fl t Ar rep-total,log-thold |
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542 messages are logged. |
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543 A DCC Reputation is computed for messages received |
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544 from IP addresses that |
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545 have sent more than |
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546 .Fl t Ar rep-total,log-thold |
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547 messages. |
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548 The DCC Reputation of an IP address is the percentage of its messages |
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549 that have been detected as bulk |
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550 or having at least 10 recipients. |
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551 The defaults are equivalent to |
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552 .Fl t Ar rep,never |
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553 and |
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554 .Fl t Ar rep-total,never,20 . |
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555 .Pp |
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556 Bad DCC Reputations do not reject mail unless enabled by an |
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557 .Ar option DCC-rep-on |
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558 line in a |
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559 .Pa whiteclnt |
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560 file. |
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561 .Pp |
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562 The checksums of locally whitelisted messages are not checked with |
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563 the DCC server and so only the number of targets of the current copy of |
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564 a whitelisted message are compared against the thresholds. |
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565 .Pp |
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566 The default is |
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567 .Ar ALL,NEVER , |
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568 so that nothing is discarded, rejected, or logged. |
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569 A common choice is |
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570 .Ar CMN,25,50 |
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571 to reject or discard |
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572 mail with common bodies except as overridden by |
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573 the whitelist of the DCC server, the sendmail |
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574 .Em ${dcc_isspam} |
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575 and |
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576 .Em ${dcc_notspam} |
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577 macros, and |
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578 .Fl g , |
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579 and |
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580 .Fl w . |
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581 .It Fl g Xo |
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582 .Sm off |
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583 .Op Ar not- |
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584 .Ar type |
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585 .Sm on |
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586 .Xc |
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587 indicates that whitelisted, |
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588 .Ar OK |
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589 or |
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590 .Ar OK2 , |
|
591 counts from the DCC server for a type of checksum are to be believed. |
|
592 They should be ignored if prefixed with |
|
593 .Ar not- . |
|
594 .Ar Type |
|
595 is one of the same set of strings as for |
|
596 .Fl t . |
|
597 Only |
|
598 .Ar IP , |
|
599 .Ar env_From , |
|
600 and |
|
601 .Ar From |
|
602 are likely choices. |
|
603 By default all three are honored, |
|
604 and hence the need for |
|
605 .Ar not- . |
|
606 .It Fl S Ar hdr |
|
607 adds to the list of substitute or locally chosen headers that |
|
608 are checked with the |
|
609 .Fl w Ar whiteclnt |
|
610 file and sent to the DCC server. |
|
611 The checksum of the last header of type |
|
612 .Ar hdr |
|
613 found in the message is checked. |
|
614 .Ar Hdr |
|
615 can be |
|
616 .Em HELO |
|
617 to specify the SMTP envelope HELO value. |
|
618 .Ar Hdr |
|
619 can also be |
|
620 .Em mail_host |
|
621 to specify the sendmail "resolved" host name from |
|
622 the Mail_from value in the SMTP envelope. |
|
623 As many as six different substitute headers can be specified, but only |
|
624 the checksum of the first of the six will be sent to the DCC server. |
|
625 .It Fl l Ar logdir |
|
626 specifies a directory in which files containing copies of messages processed by |
|
627 .Nm |
|
628 are kept. |
|
629 They can be copied to per-user directories specified with |
|
630 .Fl U . |
|
631 Information about other recipients of a message is deleted from |
|
632 the per-user copies. |
|
633 .Pp |
|
634 See the FILES section below concerning the contents of the files. |
|
635 See also the |
|
636 .Ar option log-subdirectory-{day,hour,minute} |
|
637 lines in |
|
638 .Pa whiteclnt |
|
639 files described in |
|
640 .Xr dcc 8 . |
|
641 .Pp |
|
642 The directory is relative to the DCC home directory if it is not absolute |
|
643 .It Fl R Ar rundir |
|
644 specifies the "run" directory where the UNIX domain socket and file |
|
645 containing the daemon's process ID are stored. |
|
646 The default value is @dcc_rundir@ . |
|
647 .It Fl r Ar rejection-msg |
|
648 specifies the rejection message |
|
649 in |
|
650 .Fl o |
|
651 proxy mode |
|
652 for unsolicited bulk mail or for mail temporarily blocked by |
|
653 .Em greylisting |
|
654 when |
|
655 .Fl G |
|
656 is specified. |
|
657 The first |
|
658 .Fl r Ar rejection-msg |
|
659 replaces the default bulk mail rejection message, |
|
660 .Bk -words |
|
661 "5.7.1 550 mail %ID from %CIP rejected by DCC". |
|
662 .Ek |
|
663 ." see rej_def in reply.c |
|
664 The second replaces |
|
665 .Bk -words |
|
666 "4.2.1 452 mail %ID from %CIP temporary greylist embargoed". |
|
667 .Ek |
|
668 ." see grey_def in reply.c |
|
669 The third |
|
670 .Fl r Ar rejection-msg |
|
671 replaces the default SMTP rejection message |
|
672 .Bk -words |
|
673 "5.7.1 550 %ID bad reputation; see http://commercial-dcc.rhyolite.com/cgi-bin/reps.cgi?tgt=%CIP" |
|
674 .Ek |
|
675 for mail with bad DCC Reputations. |
|
676 If |
|
677 .Ar rejection-msg |
|
678 is the zero-length string, |
|
679 the |
|
680 .Fl r |
|
681 setting is counted but the corresponding message is not changed. |
|
682 .Pp |
|
683 .Ar Rejection-msg |
|
684 can contain specific information about the mail message. |
|
685 The following strings starting with % are replaced with the corresponding |
|
686 values: |
|
687 .Bl -tag -width "%BRESULT" -offset 4n -compact |
|
688 .It %ID |
|
689 message ID such as the unique part of log file name or sendmail queue ID |
|
690 .It %CIP |
|
691 SMTP client IP address |
|
692 .It %BTYPE |
|
693 type of DNS blacklist hit, such as "SMTP client", "mail_host", or "URL NS" |
|
694 .It %BTGT |
|
695 IP address or name declared bad by DNS blacklist |
|
696 .It %BPROBE |
|
697 domain name found in DNS blacklist such as 4.3.2.10.example.com |
|
698 .It %BRESULT |
|
699 value of the %BPROBE domain name found in DNS blacklist |
|
700 .El |
|
701 .Pp |
|
702 A common alternate for the bulk mail rejection message is |
|
703 .Bk -words |
|
704 "4.7.1 451 Access denied by DCC" |
|
705 .Ek |
|
706 to tell the sending mail system to continue trying. |
|
707 Use a 4yz response with caution, because it is likely to delay for days |
|
708 a delivery failure message for false positives. |
|
709 If the rejection message |
|
710 does not start with an RFC 1893 status code and RFC 2821 reply code, |
|
711 5.7.1 and 550 or 4.2.1 and 452 are used. |
|
712 .Pp |
|
713 See also |
|
714 .Fl B Ar set:rej-msg=rejection-msg |
|
715 to set the status message for mail rejected by DNS blacklists. |
|
716 .It Fl j Ar maxjobs |
|
717 limits the number of simultaneous requests that will be processed. |
|
718 The default value is the maximum number that seems to be possible given system |
|
719 limits on open files, select() bit masks, and so forth. |
|
720 Start |
|
721 .Nm |
|
722 with |
|
723 .Fl d |
|
724 and see the starting message in the system log to see the limit. |
|
725 .It Fl B Ar dnsbl-option |
|
726 enables DNS blacklist checks of the SMTP client IP address, SMTP envelope |
|
727 Mail_From sender domain name, and of host names in URLs in the message body. |
|
728 Body URL blacklisting has too many false positives to use on |
|
729 abuse mailboxes. |
|
730 It is less effective than greylisting with |
|
731 .Xr dccm 8 |
|
732 or |
|
733 .Xr dccifd 8 |
|
734 but can be useful in situations where |
|
735 greylisting cannot be used. |
|
736 .Pp |
|
737 .Ar Dnsbl-option |
|
738 is either one of the |
|
739 .Fl B Ar set:option |
|
740 forms or |
|
741 .Bd -literal -compact -offset 4n |
|
742 .Fl B Xo |
|
743 .Sm off |
|
744 .Ar domain Oo Ar ,IPaddr |
|
745 .Op Ar /xx Op Ar ,bltype Oc |
|
746 .Sm on |
|
747 .Xc |
|
748 .Ed |
|
749 .Ar Domain |
|
750 is a DNS blacklist domain such as example.com |
|
751 that will be searched. |
|
752 .Ar IPaddr Ns Op Ar /xxx |
|
753 is the string "any" |
|
754 an IP address in the DNS blacklist |
|
755 that indicates that the mail message |
|
756 should be rejected, |
|
757 or a CIDR block covering results from the DNS blacklist. |
|
758 "127.0.0.2" is assumed if |
|
759 .Ar IPaddr |
|
760 is absent. |
|
761 IPv6 addresses can be specified with the usual colon (:) notation. |
|
762 Names can be used instead of numeric addresses. |
|
763 The type of DNS blacklist |
|
764 is specified by |
|
765 .Ar bltype |
|
766 as |
|
767 .Ar name , |
|
768 .Ar IPv4 , |
|
769 or |
|
770 .Ar IPv6 . |
|
771 Given an envelope sender domain name or a domain name in a URL of |
|
772 spam.domain.org |
|
773 and a blacklist of type |
|
774 .Ar name , |
|
775 spam.domain.org.example.com will be tried. |
|
776 Blacklist types of |
|
777 .Ar IPv4 |
|
778 and |
|
779 .Ar IPv6 |
|
780 require that the domain name in a URL sender address |
|
781 be resolved into an IPv4 or IPv6 |
|
782 address. |
|
783 The address is then written as a reversed string of decimal |
|
784 octets to check the DNS blacklist, as in 2.0.0.127.example.com, |
|
785 .Pp |
|
786 More than one blacklist can be specified and blacklists can be grouped. |
|
787 All searching within a group is stopped at the first positive result. |
|
788 .Pp |
|
789 Positive results are ignored after being logged unless an |
|
790 .Ar option\ DNSBL-on |
|
791 line appears in the global or per-user |
|
792 .Pa whiteclnt |
|
793 file. |
|
794 .Pp |
|
795 .Bl -tag -width 3n |
|
796 .It Fl B Ar set:no-client |
|
797 says that SMTP client IP addresses and reverse DNS domain names should |
|
798 not be checked in the following blacklists. |
|
799 .br |
|
800 .Fl B Ar set:client |
|
801 restores the default for the following blacklists. |
|
802 .It Fl B Ar set:no-mail_host |
|
803 says that SMTP envelope Mail_From sender domain names should |
|
804 not be checked in the following blacklists. |
|
805 .Fl B Ar set:mail_host |
|
806 restores the default. |
|
807 .It Fl B Ar set:no-URL |
|
808 says that URLs in the message body should not be checked in the |
|
809 in the following blacklists. |
|
810 .Fl B Ar set:URL |
|
811 restores the default. |
|
812 .It Fl B Ar set:no-MX |
|
813 says MX servers of sender Mail_From domain names and host names in URLs |
|
814 should not be checked in the following blacklists. |
|
815 .br |
|
816 .Fl B Ar set:MX |
|
817 restores the default. |
|
818 .It Fl B Ar set:no-NS |
|
819 says DNS servers of sender Mail_From domain names and host names in URLs |
|
820 should not be checked in the following blacklists. |
|
821 .Fl B Ar set:NS |
|
822 restores the default. |
|
823 .It Fl B Ar set:defaults |
|
824 is equivalent to all of |
|
825 .Fl B Ar set:no-temp-fail |
|
826 .Fl B Ar set:client |
|
827 .br |
|
828 .Fl B Ar set:mail_host |
|
829 .Fl B Ar set:URL |
|
830 .Fl B Ar set:MX |
|
831 and |
|
832 .Fl B Ar set:NS |
|
833 .It Fl B Ar set:group=X |
|
834 adds later DNS blacklists specified with |
|
835 .Bd -literal -compact -offset 4n |
|
836 .Fl B Xo |
|
837 .Sm off |
|
838 .Ar domain Oo Ar ,IPaddr |
|
839 .Op Ar /xx Op Ar ,bltype Oc |
|
840 .Sm on |
|
841 .Xc |
|
842 .Ed |
|
843 to group 1, 2, or 3. |
|
844 .It Fl B Ar set:debug=X |
|
845 sets the DNS blacklist logging level |
|
846 .It Fl B Ar set:msg-secs=S |
|
847 limits |
|
848 .Nm |
|
849 to |
|
850 .Ar S |
|
851 seconds total for checking all DNS blacklists. |
|
852 The default is 25. |
|
853 .It Fl B Ar set:URL-secs=S |
|
854 limits |
|
855 .Nm |
|
856 to at most |
|
857 .Ar S |
|
858 seconds resolving and checking any single URL. |
|
859 The default is 11. |
|
860 Some spam contains dozens of URLs and that |
|
861 some "spamvertised" URLs contain host names that need minutes to |
|
862 resolve. |
|
863 Busy mail systems cannot afford to spend minutes checking each incoming |
|
864 mail message. |
|
865 .It Fl B Ar set:rej-msg=rejection-msg |
|
866 sets the SMTP rejection message for the following blacklists. |
|
867 .Ar Rejection-msg |
|
868 must be in the same format as for |
|
869 .Fl r . |
|
870 If |
|
871 .Ar rejection-msg |
|
872 is null, the default is restored. |
|
873 The default DNS blacklist rejection message is the first message set |
|
874 with |
|
875 .Fl r . |
|
876 .It Fl B Ar set:temp-fail |
|
877 causes |
|
878 .Nm |
|
879 to the MTA to answer the SMTP DATA command with |
|
880 .Bd -literal -offset 3n -compact |
|
881 452 4.2.1 mail %ID from %CIP temporary delayed for DNSBL |
|
882 .Ed |
|
883 if any DNS answer required for a DNSBL in the current group times out, |
|
884 including resolving names in URLs. |
|
885 .It Fl B Ar set:no-temp-fail |
|
886 restores the default of assuming a negative answer for DNS responses |
|
887 that take too long. |
|
888 .It Fl B Ar set:maxjobs=X |
|
889 sets maximum number of helper processes to |
|
890 .Ar X . |
|
891 In order to use typical single-threaded DNS resolver libraries, |
|
892 .Nm |
|
893 uses fleets of helper processes. |
|
894 It is rarely a good idea to change the default, |
|
895 which is the same as the maximum number of simultaneous jobs set with |
|
896 .Fl j . |
|
897 .It Fl B Ar set:progpath=@libexecdir@/dns-helper |
|
898 changes the path to the helper program. |
|
899 .El |
|
900 .It Fl L Ar ltype,facility.level |
|
901 specifies how messages should be logged. |
|
902 .Ar Ltype |
|
903 must be |
|
904 .Ar error , |
|
905 .Ar info , |
|
906 or |
|
907 .Ar off |
|
908 to indicate which of the two types of messages are being controlled or |
|
909 to turn off all |
|
910 .Xr syslog 3 |
|
911 messages from |
|
912 .Nm . |
|
913 .Ar Level |
|
914 must be a |
|
915 .Xr syslog 3 |
|
916 level among |
|
917 .Ar EMERG , |
|
918 .Ar ALERT , |
|
919 .Ar CRIT , ERR , |
|
920 .Ar WARNING , |
|
921 .Ar NOTICE , |
|
922 .Ar INFO , |
|
923 and |
|
924 .Ar DEBUG . |
|
925 .Ar Facility |
|
926 must be among |
|
927 .Ar AUTH , |
|
928 .Ar AUTHPRIV , |
|
929 .Ar CRON , |
|
930 .Ar DAEMON , |
|
931 .Ar FTP , |
|
932 .Ar KERN , |
|
933 .Ar LPR , |
|
934 .Ar MAIL , |
|
935 .Ar NEWS , |
|
936 .Ar USER , |
|
937 .Ar UUCP , |
|
938 and |
|
939 .Ar LOCAL0 |
|
940 through |
|
941 .Ar LOCAL7 . |
|
942 The default is equivalent to |
|
943 .Dl Fl L Ar info,MAIL.NOTICE Fl L Ar error,MAIL.ERR |
|
944 .El |
|
945 .Pp |
|
946 .Nm |
|
947 normally sends counts of mail rejected and so forth the to system log at |
|
948 midnight. |
|
949 The SIGUSR1 signal sends an immediate report to the system log. |
|
950 They will be repeated every 24 hours instead of at midnight. |
|
951 .Sh SENDMAIL MACROS |
|
952 Sendmail can affect |
|
953 .Nm |
|
954 with the values of some |
|
955 .Pa sendmail.cf |
|
956 macros. |
|
957 These macro names must be added to the |
|
958 Milter.macros option statements in |
|
959 .Pa sendmail.cf |
|
960 as in the example "Feature" file dcc.m4. |
|
961 .Bl -tag -width dcc_mail_host |
|
962 .It Em ${dcc_isspam} |
|
963 causes a mail message to be reported to the DCC server |
|
964 as having been addressed to "MANY" recipients. |
|
965 The |
|
966 .Em ${dcc_isspam} |
|
967 macro is ignored if the |
|
968 .Em ${dcc_notspam} |
|
969 macro is set to a non-null string |
|
970 .Pp |
|
971 If the value of the |
|
972 .Ar ${dcc_isspam} |
|
973 is null, |
|
974 .Nm |
|
975 uses SMTP rejection messages controlled by |
|
976 .Fl a |
|
977 and |
|
978 .Fl r . |
|
979 If the value of the |
|
980 .Ar ${dcc_isspam} |
|
981 macro starts with "DISCARD", |
|
982 the mail message is silently discarded |
|
983 as with |
|
984 .Fl a Ar DISCARD. |
|
985 If value of the macro not null and does not start with "DISCARD", |
|
986 it is used as the SMTP error |
|
987 message given to the SMTP client trying to send the rejected message. |
|
988 The message starts with an optional SMTP error type and number |
|
989 followed by text. |
|
990 .Pp |
|
991 The |
|
992 .Fl a |
|
993 option does not effect messages |
|
994 marked spam with |
|
995 .Em ${dcc_isspam} . |
|
996 When the |
|
997 .Em ${dcc_isspam} |
|
998 macro is set, the message is rejected or discarded despite |
|
999 local or DCC database whitelist entries. |
|
1000 The local whitelist does control whether the message's |
|
1001 checksums will be reported to the DCC server and an |
|
1002 .Em X-DCC |
|
1003 SMTP header line will be added. |
|
1004 .It Em ${dcc_notspam} |
|
1005 causes a message not be considered unsolicited bulk despite |
|
1006 evidence to the contrary. |
|
1007 It also prevents |
|
1008 .Nm |
|
1009 from reporting the checksums of the message to the DCC server |
|
1010 and from adding an |
|
1011 .Em X-DCC |
|
1012 header line. |
|
1013 .Pp |
|
1014 When the macro is set by the |
|
1015 .Pa sendmail.cf |
|
1016 rules, |
|
1017 .Ar ${dcc_notspam} |
|
1018 macros overrides DCC threshlds that say the message should be |
|
1019 rejected as well as the effects of the |
|
1020 .Em ${dcc_isspam} |
|
1021 macro. |
|
1022 .It Em ${dcc_mail_host} |
|
1023 specifies the name of the SMTP client that is sending the message. |
|
1024 This macro is usually the same as the |
|
1025 .Em mail_host |
|
1026 macro. |
|
1027 They can differ when a sendmail "smart relay" is involved. |
|
1028 The |
|
1029 .Em ${dcc_mail_host} |
|
1030 macro does not work if |
|
1031 .Em FEATURE(delay_checks) |
|
1032 is used. |
|
1033 .It Em ${dcc_userdir} |
|
1034 is the per-user whitelist and log directory for a recipient. |
|
1035 If the macro is not set in sendmail.cf, |
|
1036 $&{rcpt_mailer}/$&{rcpt_addr} |
|
1037 is assumed, but with the recipient address converted to lower case. |
|
1038 Whatever value is used, |
|
1039 the directory name after the last slash (/) character is converted to |
|
1040 lower case. |
|
1041 Any value containing the string "/../" is ignored. |
|
1042 .Pp |
|
1043 This macro also does not work if |
|
1044 .Em FEATURE(delay_checks) |
|
1045 is used. |
|
1046 .Pp |
|
1047 The following two lines in a sendmail mc file have the same effect |
|
1048 as not defining the ${dcc_userdir} macro, provided |
|
1049 .Em FEATURE(dcc) |
|
1050 is also used and |
|
1051 the sendmail |
|
1052 .Pa cf/feature |
|
1053 directory has a symbolic link to the |
|
1054 .Pa misc/dcc.m4 |
|
1055 file. |
|
1056 .El |
|
1057 .Pp |
|
1058 .Bd -literal -compact |
|
1059 SLocal_check_rcpt |
|
1060 R$* $: $1 $(macro {dcc_userdir} $@ $&{rcpt_mailer}/$&{rcpt_addr} $)) |
|
1061 .Ed |
|
1062 .Sh FILES |
|
1063 .Bl -tag -width whiteclnt -compact |
|
1064 .It Pa @prefix@ |
|
1065 is the DCC home directory in which other files are found. |
|
1066 .It Pa @libexecdir@/start-dccm |
|
1067 is a script used to |
|
1068 .Nm . |
|
1069 .It Pa dcc/dcc_conf |
|
1070 contains parameters used by the scripts to start DCC daemons and cron jobs. |
|
1071 .It Pa logdir |
|
1072 is an optional directory specified with |
|
1073 .Fl l |
|
1074 and containing marked mail. |
|
1075 Each file in the directory contains one message, at least one of whose |
|
1076 checksums reached its |
|
1077 .Fl t |
|
1078 thresholds or that is interesting for some other reason. |
|
1079 Each file starts with lines containing the date when the message |
|
1080 was received, the IP address of the SMTP client, and SMTP envelope |
|
1081 values. |
|
1082 Those lines are followed by the body of the SMTP message including its header |
|
1083 as it was received by sendmail and without any new or changed header lines. |
|
1084 Only approximately the first 32 KBytes of the body are recorded |
|
1085 unless modified by |
|
1086 .Em ./configure --with-max-log-size=xx |
|
1087 The checksums for the message follow the body. |
|
1088 They are followed by lines indicating that the |
|
1089 .Em ${dcc_isspam} |
|
1090 or |
|
1091 .Em ${dcc_notspam} |
|
1092 .Pa sendmail.cf |
|
1093 macros were set or one of the checksums is white- or blacklisted by the |
|
1094 .Fl w Ar whiteclnt |
|
1095 file. |
|
1096 Each file ends with the |
|
1097 .Em X-DCC |
|
1098 header line added to the message and the disposition of |
|
1099 the message including SMTP status message if appropriate. |
|
1100 .It Pa map |
|
1101 is the memory mapped file of information concerning DCC servers |
|
1102 in the DCC home directory. |
|
1103 .It Pa whiteclnt |
|
1104 contains the client whitelist in |
|
1105 the format described in |
|
1106 .Xr dcc 8 . |
|
1107 .It Pa whiteclnt.dccw |
|
1108 is a memory mapped hash table of the |
|
1109 .Pa whiteclnt |
|
1110 file. |
|
1111 .It Pa dccm.pid |
|
1112 in the |
|
1113 .Fl R Ar rundir |
|
1114 directory contains daemon's process ID. |
|
1115 The string |
|
1116 .Dq dccm |
|
1117 is replaced by the file name containing the daemon to facilitate |
|
1118 running multiple daemons, probably connected to remote instances of |
|
1119 sendmail using TCP/IP instead of a UNIX domain socket. |
|
1120 See also |
|
1121 .Fl R . |
|
1122 .It Pa @dcc_rundir@/dccm |
|
1123 is the default UNIX domain socket used by the sendmail milter interface. |
|
1124 See also |
|
1125 .Fl R . |
|
1126 .It Pa sendmail.cf |
|
1127 is the |
|
1128 .Xr sendmail 8 |
|
1129 control file. |
|
1130 .It Pa misc/dcc.m4 |
|
1131 sendmail mc file that should have a symbolic link in the sendmail |
|
1132 cf/feature directory so that |
|
1133 .Em FEATURE(dcc) |
|
1134 can be used in a sendmail mc file. |
|
1135 .El |
|
1136 .Sh EXAMPLES |
|
1137 .Nm Dccm |
|
1138 should be started before sendmail with something like the |
|
1139 script |
|
1140 .Pa @libexecdir@/start-dccm. |
|
1141 It looks for common DCC parameters in the |
|
1142 .Pa dcc_conf |
|
1143 file in the DCC home directory, |
|
1144 .Pa @prefix@. |
|
1145 .Pp |
|
1146 Those numbers should modified to fit local conditions. |
|
1147 It might be wise to replace the "100" numbers with much larger |
|
1148 values or with "MANY" until a few weeks of monitoring the log directory |
|
1149 show that sources of mailing lists are in the server's whitelist file |
|
1150 (see |
|
1151 .Xr dccd 8 ) |
|
1152 or the local |
|
1153 .Pa whiteclnt |
|
1154 file. |
|
1155 .Pp |
|
1156 It is usually necessary to regularly delete old log files |
|
1157 with a script like @libexecdir@/cron-dccd. |
|
1158 .Pp |
|
1159 On systems unlike modern FreeBSD and other UNIX-like systems which |
|
1160 include sendmail milter support, |
|
1161 sendmail must be built with the milter interface, such as by creating a |
|
1162 .Pa devtools/Site/site.config.m4 |
|
1163 or similar file containing something like the following lines: |
|
1164 .Bd -literal -offset indent |
|
1165 APPENDDEF(`conf_sendmail_ENVDEF', `-D_FFR_MILTER=1') |
|
1166 APPENDDEF(`conf_libmilter_ENVDEF', `-D_FFR_MILTER=1') |
|
1167 .Ed |
|
1168 .Pp |
|
1169 Appropriate lines invoking the milter interface must be added to |
|
1170 .Pa sendmail.cf. |
|
1171 That can be done by putting a symbolic link to the |
|
1172 the misc/dcc.m4 file in the DCC source to the sendmail cf/feature directory |
|
1173 and adding the line |
|
1174 .Pp |
|
1175 .Dl FEATURE(dcc) |
|
1176 .Pp |
|
1177 to the local .mc file. |
|
1178 .Pp |
|
1179 Note that |
|
1180 .Nm |
|
1181 should not be used with the Postfix milter mechanism. |
|
1182 Instead use |
|
1183 .Xr dccifd 8 |
|
1184 as a before-queue filter as described in that man page. |
|
1185 .Sh SEE ALSO |
|
1186 .Xr cdcc 8 , |
|
1187 .Xr dbclean 8 , |
|
1188 .Xr dcc 8 , |
|
1189 .Xr dccd 8 , |
|
1190 .Xr dblist 8 , |
|
1191 .Xr dccifd 8 , |
|
1192 .Xr dccproc 8 , |
|
1193 .Xr dccsight 8 , |
|
1194 .Xr sendmail 8 . |
|
1195 .Sh HISTORY |
|
1196 Distributed Checksum Clearinghouses are based on an idea of Paul Vixie. |
|
1197 Implementation of |
|
1198 .Nm |
|
1199 was started at Rhyolite Software in 2000. |
|
1200 This document describes version 1.3.103. |
|
1201 .Sh BUGS |
|
1202 .Nm |
|
1203 uses |
|
1204 .Fl t |
|
1205 where |
|
1206 .Xr dccproc 8 |
|
1207 uses |
|
1208 .Fl c . |
|
1209 .Pp |
|
1210 Systems without |
|
1211 .Xr setrlimit 2 |
|
1212 and |
|
1213 .Xr getrlimit 2 |
|
1214 RLIMIT_NOFILE |
|
1215 can have problems with the default limit on the number of simultaneous |
|
1216 jobs, the value of |
|
1217 .Fl j . |
|
1218 Every job requires four open files. |
|
1219 These problems are usually seen with errors messages that say something like |
|
1220 .Dl dccm[24448]: DCC: accept() returned invalid socket |
|
1221 A fix is to use a smaller value for |
|
1222 .Fl j |
|
1223 or to allow |
|
1224 .Nm |
|
1225 to open more files. |
|
1226 Sendmail version 8.13 and later can be told to poll() instead of select |
|
1227 with SM_CONF_POLL. |
|
1228 Some older versions of sendmail knew about FFR_USE_POLL. |
|
1229 One of the following lines in your devtools/Site/site.config.m4 |
|
1230 file can help: |
|
1231 .Bd -literal -offset indent |
|
1232 APPENDDEF(`conf_libmilter_ENVDEF', `-DSM_CONF_POLL') |
|
1233 APPENDDEF(`conf_libmilter_ENVDEF', `-DFFR_USE_POLL') |
|
1234 .Ed |
|
1235 .Pp |
|
1236 On many systems with sendmail 8.11.3 and preceding, |
|
1237 a bug in the sendmail milter mechanism causes |
|
1238 .Nm |
|
1239 to die with a core file when given a signal. |