VERP_README.html revision 1.1.1.6
1 1.1 tron <!doctype html public "-//W3C//DTD HTML 4.01 Transitional//EN" 2 1.1.1.6 christos "https://www.w3.org/TR/html4/loose.dtd"> 3 1.1 tron 4 1.1 tron <html> 5 1.1 tron 6 1.1 tron <head> 7 1.1 tron 8 1.1 tron <title>Postfix VERP Howto</title> 9 1.1 tron 10 1.1.1.4 christos <meta http-equiv="Content-Type" content="text/html; charset=utf-8"> 11 1.1.1.5 christos <link rel='stylesheet' type='text/css' href='postfix-doc.css'> 12 1.1 tron 13 1.1 tron </head> 14 1.1 tron 15 1.1 tron <body> 16 1.1 tron 17 1.1 tron <h1><img src="postfix-logo.jpg" width="203" height="98" ALT="">Postfix VERP Howto</h1> 18 1.1 tron 19 1.1 tron <hr> 20 1.1 tron 21 1.1 tron <h2>Postfix VERP support</h2> 22 1.1 tron 23 1.1 tron <p> Postfix versions 1.1 and later support variable envelope return 24 1.1 tron path addresses on request. When VERP style delivery is requested, 25 1.1 tron each recipient of a message receives a customized copy of the 26 1.1 tron message, with his/her own recipient address encoded in the envelope 27 1.1 tron sender address. </p> 28 1.1 tron 29 1.1 tron <p> For example, when VERP style delivery is requested, Postfix 30 1.1 tron delivers mail from "<tt>owner-listname@origin</tt>" for a recipient 31 1.1 tron "<tt>user@domain</tt>", with a sender address that encodes the 32 1.1 tron recipient as follows: </p> 33 1.1 tron 34 1.1 tron <blockquote> 35 1.1 tron <pre> 36 1.1 tron owner-listname+user=domain@origin 37 1.1 tron </pre> 38 1.1 tron </blockquote> 39 1.1 tron 40 1.1 tron <p> Thus, undeliverable mail can reveal the undeliverable recipient 41 1.1 tron address without requiring the list owner to parse bounce messages. 42 1.1 tron </p> 43 1.1 tron 44 1.1 tron <p> The VERP concept was popularized by the qmail MTA and by the ezmlm 45 1.1.1.6 christos mailing list manager. See <a href="https://cr.yp.to/proto/verp.txt">https://cr.yp.to/proto/verp.txt</a> for the 46 1.1 tron ideas behind this concept. </p> 47 1.1 tron 48 1.1 tron <p> Topics covered in this document: </p> 49 1.1 tron 50 1.1 tron <ul> 51 1.1 tron 52 1.1 tron <li> <a href="#config"> Postfix VERP configuration parameters </a> 53 1.1 tron 54 1.1 tron <li> <a href="#majordomo"> Using VERP with majordomo etc. mailing lists </a> 55 1.1 tron 56 1.1 tron <li> <a href="#smtp"> VERP support in the Postfix SMTP server</a> 57 1.1 tron 58 1.1 tron <li> <a href="#sendmail"> VERP support in the Postfix sendmail command </a> 59 1.1 tron 60 1.1 tron <li> <a href="#qmqp"> VERP support in the Postfix QMQP server </a> 61 1.1 tron 62 1.1 tron </ul> 63 1.1 tron 64 1.1 tron <h2> <a name="config"> Postfix VERP configuration parameters </a> </h2> 65 1.1 tron 66 1.1 tron With Postfix, the whole process is controlled by four configuration 67 1.1 tron parameters. 68 1.1 tron 69 1.1 tron <dl> 70 1.1 tron 71 1.1 tron <dt> <a href="postconf.5.html#default_verp_delimiters">default_verp_delimiters</a> (default value: +=) 72 1.1 tron 73 1.1 tron <dd> <p> What VERP delimiter characters Postfix uses when VERP 74 1.1 tron style delivery is requested but no explicit delimiters are 75 1.1 tron specified. </p> 76 1.1 tron 77 1.1 tron <dt> <a href="postconf.5.html#verp_delimiter_filter">verp_delimiter_filter</a> (default: -+=) 78 1.1 tron 79 1.1 tron <dd> <p> What characters Postfix accepts as VERP delimiter 80 1.1 tron characters on the sendmail command line and in SMTP commands. 81 1.1 tron Many characters must not be used as VERP delimiter characters, 82 1.1 tron either because they already have a special meaning in email 83 1.1 tron addresses (such as the @ or the %), because they are used as 84 1.1 tron part of a username or domain name (such as alphanumerics), or 85 1.1 tron because they are non-ASCII or control characters. And who 86 1.1 tron knows, some characters may tickle bugs in vulnerable software, 87 1.1 tron and we would not want that to happen. </p> </dd> 88 1.1 tron 89 1.1 tron <dt> <a href="postconf.5.html#smtpd_authorized_verp_clients">smtpd_authorized_verp_clients</a> (default value: none) 90 1.1 tron 91 1.1 tron <dd> <p> What SMTP clients are allowed to request VERP style 92 1.1 tron delivery. The Postfix QMQP server uses its own access control 93 1.1 tron mechanism, and local submission (via /usr/sbin/sendmail etc.) 94 1.1 tron is always authorized. To authorize a host, list its name, IP 95 1.1 tron address, subnet (net/mask) or parent .domain. </p> 96 1.1 tron 97 1.1 tron <p> With Postfix versions 1.1 and 2.0, this parameter is called 98 1.1 tron <a href="postconf.5.html#authorized_verp_clients">authorized_verp_clients</a> (default: $<a href="postconf.5.html#mynetworks">mynetworks</a>). </p> </dd> 99 1.1 tron 100 1.1 tron <dt> <a href="postconf.5.html#disable_verp_bounces">disable_verp_bounces</a> (default: no) 101 1.1 tron 102 1.1.1.2 tron <dd> <p> Send one bounce report for multi-recipient VERP mail, 103 1.1.1.2 tron instead of one bounce report per recipient. The default, 104 1.1 tron one per recipient, is what ezmlm needs. </p> </dd> 105 1.1 tron 106 1.1 tron </dl> 107 1.1 tron 108 1.1 tron <h2> <a name="majordomo"> Using VERP with majordomo etc. mailing lists </a> </h2> 109 1.1 tron 110 1.1 tron <p> In order to make VERP useful with majordomo etc. mailing lists, 111 1.1 tron you would configure the list manager to submit mail according 112 1.1 tron to one of the following two forms: </p> 113 1.1 tron 114 1.1 tron <p> Postfix 2.3 and later: </p> 115 1.1 tron 116 1.1 tron <blockquote> 117 1.1 tron <pre> 118 1.1 tron % sendmail -XV -f owner-listname other-arguments... 119 1.1 tron 120 1.1 tron % sendmail -XV+= -f owner-listname other-arguments... 121 1.1 tron </pre> 122 1.1 tron </blockquote> 123 1.1 tron 124 1.1 tron <p> Postfix 2.2 and earlier (Postfix 2.3 understands the old syntax 125 1.1 tron for backwards compatibility, but will log a warning that reminds 126 1.1 tron you of the new syntax): </p> 127 1.1 tron 128 1.1 tron <blockquote> 129 1.1 tron <pre> 130 1.1 tron % sendmail -V -f owner-listname other-arguments... 131 1.1 tron 132 1.1 tron % sendmail -V+= -f owner-listname other-arguments... 133 1.1 tron </pre> 134 1.1 tron </blockquote> 135 1.1 tron 136 1.1 tron <p> The first form uses the default <a href="postconf.5.html">main.cf</a> VERP delimiter characters. 137 1.1 tron The second form allows you to explicitly specify the VERP delimiter 138 1.1 tron characters. The example shows the recommended values. </p> 139 1.1 tron 140 1.1 tron <p> This text assumes that you have set up an owner-listname alias 141 1.1 tron that routes undeliverable mail to a real person: </p> 142 1.1 tron 143 1.1 tron <blockquote> 144 1.1 tron <pre> 145 1.1 tron /etc/aliases: 146 1.1 tron owner-listname: yourname+listname 147 1.1 tron </pre> 148 1.1 tron </blockquote> 149 1.1 tron 150 1.1 tron <p> In order to process bounces we are going to make extensive use 151 1.1 tron of address extension tricks. </p> 152 1.1 tron 153 1.1 tron <p> You need to tell Postfix that + is the separator between an 154 1.1 tron address and its optional address extension, that address extensions 155 1.1 tron are appended to .forward file names, and that address extensions 156 1.1 tron are to be discarded when doing alias expansions: </p> 157 1.1 tron 158 1.1 tron <blockquote> 159 1.1 tron <pre> 160 1.1 tron /etc/postfix/<a href="postconf.5.html">main.cf</a>: 161 1.1 tron <a href="postconf.5.html#recipient_delimiter">recipient_delimiter</a> = + 162 1.1 tron <a href="postconf.5.html#forward_path">forward_path</a> = $home/.forward${<a href="postconf.5.html#recipient_delimiter">recipient_delimiter</a>}${extension}, 163 1.1 tron $home/.forward 164 1.1 tron <a href="postconf.5.html#propagate_unmatched_extensions">propagate_unmatched_extensions</a> = canonical, virtual 165 1.1 tron </pre> 166 1.1 tron </blockquote> 167 1.1 tron 168 1.1 tron <p> (the last two parameter settings are default settings). </p> 169 1.1 tron 170 1.1 tron <p> You need to set up a file named .forward+listname with the 171 1.1 tron commands that process all the mail that is sent to the owner-listname 172 1.1 tron address: </p> 173 1.1 tron 174 1.1 tron <blockquote> 175 1.1 tron <pre> 176 1.1 tron ~/.forward+listname: 177 1.1 tron "|/some/where/command ..." 178 1.1 tron </pre> 179 1.1 tron </blockquote> 180 1.1 tron 181 1.1 tron <p> With this set up, undeliverable mail for user@domain will be returned 182 1.1 tron to the following address: </p> 183 1.1 tron 184 1.1 tron <blockquote> 185 1.1 tron <pre> 186 1.1 tron owner-listname+user=domain (a] your.domain 187 1.1 tron </pre> 188 1.1 tron </blockquote> 189 1.1 tron 190 1.1 tron <p> which is processed by the command in your .forward+listname file. 191 1.1 tron The message should contain, among others, a To: header with the 192 1.1 tron encapsulated recipient sender address: </p> 193 1.1 tron 194 1.1 tron <blockquote> 195 1.1 tron <pre> 196 1.1 tron To: owner-listname+user=domain (a] your.domain 197 1.1 tron </pre> 198 1.1 tron </blockquote> 199 1.1 tron 200 1.1 tron <p> It is left as an exercise for the reader to parse the To: header 201 1.1 tron line and to pull out the user=domain part from the recipient address. 202 1.1 tron </p> 203 1.1 tron 204 1.1 tron <h2> <a name="smtp"> VERP support in the Postfix SMTP server </a> </h2> 205 1.1 tron 206 1.1 tron <p> The Postfix SMTP server implements a command XVERP to enable 207 1.1 tron VERP style delivery. The syntax allows two forms: </p> 208 1.1 tron 209 1.1 tron <blockquote> 210 1.1 tron <pre> 211 1.1 tron MAIL FROM:<sender@domain> XVERP 212 1.1 tron 213 1.1 tron MAIL FROM:<sender@domain> XVERP=+= 214 1.1 tron </pre> 215 1.1 tron </blockquote> 216 1.1 tron 217 1.1 tron <p> The first form uses the default <a href="postconf.5.html">main.cf</a> VERP delimiters, the 218 1.1 tron second form overrides them explicitly. The values shown are the 219 1.1 tron recommended ones. </p> 220 1.1 tron 221 1.1.1.2 tron <p> You can use the <a href="postconf.5.html#smtpd_command_filter">smtpd_command_filter</a> feature to append XVERP 222 1.1.1.3 tron to SMTP commands from legacy software. This requires Postfix 2.7 223 1.1.1.2 tron or later. </p> 224 1.1.1.2 tron 225 1.1.1.2 tron <blockquote> 226 1.1.1.2 tron <pre> 227 1.1.1.2 tron /etc/postfix/<a href="postconf.5.html">main.cf</a>: 228 1.1.1.2 tron <a href="postconf.5.html#smtpd_command_filter">smtpd_command_filter</a> = <a href="pcre_table.5.html">pcre</a>:/etc/postfix/append_verp.pcre 229 1.1.1.2 tron <a href="postconf.5.html#smtpd_authorized_verp_clients">smtpd_authorized_verp_clients</a> = $<a href="postconf.5.html#mynetworks">mynetworks</a> 230 1.1.1.2 tron 231 1.1.1.2 tron /etc/postfix/append_verp.<a href="pcre_table.5.html">pcre</a>: 232 1.1.1.2 tron /^(MAIL FROM:<listname@example\.com>.*)/ $1 XVERP 233 1.1.1.2 tron </pre> 234 1.1.1.2 tron </blockquote> 235 1.1.1.2 tron 236 1.1 tron <h2> <a name="sendmail"> VERP support in the Postfix sendmail command </a> </h2> 237 1.1 tron 238 1.1 tron <p> The Postfix sendmail command has a -V flag to request VERP style 239 1.1 tron delivery. Specify one of the following two forms: </p> 240 1.1 tron 241 1.1 tron <p> Postfix 2.3 and later:</p> 242 1.1 tron <blockquote> 243 1.1 tron <pre> 244 1.1 tron % sendmail -XV -f owner-listname .... 245 1.1 tron 246 1.1 tron % sendmail -XV+= -f owner-listname .... 247 1.1 tron </pre> 248 1.1 tron </blockquote> 249 1.1 tron 250 1.1 tron <p> Postfix 2.2 and earlier (Postfix 2.3 understands the old syntax 251 1.1 tron for backwards compatibility, but will log a warning that reminds 252 1.1 tron you of the new syntax): </p> 253 1.1 tron 254 1.1 tron <blockquote> 255 1.1 tron <pre> 256 1.1 tron % sendmail -V -f owner-listname .... 257 1.1 tron 258 1.1 tron % sendmail -V+= -f owner-listname .... 259 1.1 tron </pre> 260 1.1 tron </blockquote> 261 1.1 tron 262 1.1 tron <p> The first form uses the default <a href="postconf.5.html">main.cf</a> VERP delimiters, the 263 1.1 tron second form overrides them explicitly. The values shown are the 264 1.1 tron recommended ones. </p> 265 1.1 tron 266 1.1 tron <h2> <a name="qmqp"> VERP support in the Postfix QMQP server </a> </h2> 267 1.1 tron 268 1.1 tron <p> When the Postfix QMQP server receives mail with an envelope 269 1.1 tron sender address of the form: </p> 270 1.1 tron 271 1.1 tron <blockquote> 272 1.1 tron <pre> 273 1.1 tron listname- (a] your.domain-@[] 274 1.1 tron </pre> 275 1.1 tron </blockquote> 276 1.1 tron 277 1.1 tron <p> Postfix generates sender addresses 278 1.1 tron "<tt>listname-user=domain (a] your.domain</tt>", using "-=" as the VERP 279 1.1 tron delimiters because qmail/ezmlm expect this. </p> 280 1.1 tron 281 1.1 tron <p> More generally, a sender address of "<tt>prefix@origin-@[]</tt>" 282 1.1 tron requests VERP style delivery with sender addresses of the form 283 1.1 tron "<tt>prefixuser=domain@origin</tt>". However, Postfix allows only 284 1.1 tron VERP delimiters that are specified with the <a href="postconf.5.html#verp_delimiter_filter">verp_delimiter_filter</a> 285 1.1 tron parameter. In particular, the "=" delimiter is required for qmail 286 1.1 tron compatibility (see the qmail addresses(5) manual page for details). 287 1.1 tron 288 1.1 tron </body> 289 1.1 tron 290 1.1 tron </html> 291
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