postfix-master/VIRTUAL_README.html

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  16 <h1><img src="postfix-logo.jpg" width="203" height="98" ALT="">Postfix
  17 Virtual Domain Hosting Howto</h1>
  18
  19 <hr>
  20
  21 <h2>Purpose of this document</h2>
  22
  23 <p> This document requires Postfix version 2.0 or later. </p>
  24
  25 <p> This document gives an overview of how Postfix can be used for
  26 hosting multiple Internet domains, both for final delivery on the
  27 machine itself and for the purpose of forwarding to destinations
  28 elsewhere. </p>
  29
  30 <p> The text not only describes delivery mechanisms that are built
  31 into Postfix, but also gives pointers for using non-Postfix mail
  32 delivery software. </p>
  33
  34 <p> The following topics are covered: </p>
  35
  36 <ul>
  37
  38 <li> <a href="#canonical">Canonical versus hosted versus other domains</a>
  39
  40 <li> <a href="#local_vs_database">Local files versus network databases</a>
  41
  42 <li> <a href="#local">As simple as can be: shared domains,
  43 UNIX system accounts</a>
  44
  45 <li> <a href="#virtual_alias">Postfix virtual ALIAS example:
  46 separate domains, UNIX system accounts</a>
  47
  48 <li> <a href="#virtual_mailbox">Postfix virtual MAILBOX example:
  49 separate domains, non-UNIX accounts</a>
  50
  51 <li> <a href="#in_virtual_other">Non-Postfix mailbox store: separate
  52 domains, non-UNIX accounts</a>
  53
  54 <li> <a href="#forwarding">Mail forwarding domains</a>
  55
  56 <li> <a href="#mailing_lists">Mailing lists</a>
  57
  58 <li> <a href="#autoreplies">Autoreplies</a>
  59
  60 </ul>
  61
  62 <h2><a name="canonical">Canonical versus hosted versus
  63 other domains</a></h2>
  64
  65 <p>Most Postfix systems are <b>final destination</b> for only a
  66 few domain names.  These include the hostnames and [the IP addresses]
  67 of the machine that Postfix runs on, and sometimes also include
  68 the parent domain of the hostname.  The remainder of this document
  69 will refer to these domains as the <a href="VIRTUAL_README.html#canonical">canonical domains</a>. They are
  70 usually implemented with the Postfix <a href="ADDRESS_CLASS_README.html#local_domain_class">local domain</a> address class,
  71 as defined in the <a href="ADDRESS_CLASS_README.html">ADDRESS_CLASS_README</a> file.</p>
  72
  73 <p> Besides the <a href="VIRTUAL_README.html#canonical">canonical domains</a>, Postfix can be configured to be
  74 <b>final destination</b> for any number of additional domains.
  75 These domains are called hosted, because they are not directly
  76 associated with the name of the machine itself. Hosted domains are
  77 usually implemented with the <a href="ADDRESS_CLASS_README.html#virtual_alias_class">virtual alias domain</a> address class
  78 and/or with the <a href="ADDRESS_CLASS_README.html#virtual_mailbox_class">virtual mailbox domain</a> address class, as defined
  79 in the <a href="ADDRESS_CLASS_README.html">ADDRESS_CLASS_README</a> file. </p>
  80
  81 <p> But wait! There is more. Postfix can be configured as a backup
  82 MX host for other domains. In this case Postfix is <b>not the final
  83 destination</b> for those domains. It merely queues the mail when
  84 the primary MX host is down, and forwards the mail when the primary
  85 MX host becomes available. This function is implemented with the
  86 <a href="ADDRESS_CLASS_README.html#relay_domain_class">relay domain</a> address class, as defined in the <a href="ADDRESS_CLASS_README.html">ADDRESS_CLASS_README</a>
  87 file.  </p>
  88
  89 <p> Finally, Postfix can be configured as a transit host for sending
  90 mail across the internet. Obviously, Postfix is not final destination
  91 for such mail. This function is available only for authorized
  92 clients and/or users, and is implemented by the <a href="ADDRESS_CLASS_README.html#default_domain_class">default domain</a>
  93 address class, as defined in the <a href="ADDRESS_CLASS_README.html">ADDRESS_CLASS_README</a> file. </p>
  94
  95 <h2><a name="local_vs_database">Local files versus network databases</a></h2>
  96
  97 <p> The examples in this text use table lookups from local files
  98 such as DBM or Berkeley DB.  These are easy to debug with the
  99 <b>postmap</b> command: </p>
 100
 101 <blockquote>
 102 Example: <tt>postmap -q info@example.com hash:/etc/postfix/virtual</tt>
 103 </blockquote>
 104
 105 <p> See the documentation in <a href="LDAP_README.html">LDAP_README</a>, <a href="MYSQL_README.html">MYSQL_README</a> and <a href="PGSQL_README.html">PGSQL_README</a>
 106 for how to replace local files by databases. The reader is strongly
 107 advised to make the system work with local files before migrating
 108 to network databases, and to use the <b>postmap</b> command to verify
 109 that network database lookups produce the exact same results as
 110 local file lookup. </p>
 111
 112 <blockquote>
 113 Example: <tt>postmap -q info@example.com <a href="ldap_table.5.html">ldap</a>:/etc/postfix/virtual.cf</tt>
 114 </blockquote>
 115
 116 <h2><a name="local">As simple as can be: shared domains, UNIX system
 117 accounts</a></h2>
 118
 119 <p> The simplest method to host an additional domain is to add the
 120 domain name to the domains listed in the Postfix <a href="postconf.5.html#mydestination">mydestination</a>
 121 configuration parameter, and to add the user names to the UNIX
 122 password file. </p>
 123
 124 <p> This approach makes no distinction between canonical and hosted
 125 domains. Each username can receive mail in every domain. </p>
 126
 127 <p> In the examples we will use "example.com" as the domain that is
 128 being hosted on the local Postfix machine. </p>
 129
 130 <blockquote>
 131 <pre>
 132 /etc/postfix/<a href="postconf.5.html">main.cf</a>:
 133     <a href="postconf.5.html#mydestination">mydestination</a> = $<a href="postconf.5.html#myhostname">myhostname</a> localhost.$<a href="postconf.5.html#mydomain">mydomain</a> ... example.com
 134 </pre>
 135 </blockquote>
 136
 137 <p> The limitations of this approach are: </p>
 138
 139 <ul>
 140
 141 <li>A total lack of separation: mail for info@my.host.name is
 142 delivered to the same UNIX system account as mail for info@example.com.
 143
 144 <li> With users in the UNIX password file, administration of large
 145 numbers of users becomes inconvenient.
 146
 147 </ul>
 148
 149 <p> The examples that follow provide solutions for both limitations.
 150 </p>
 151
 152 <h2><a name="virtual_alias">Postfix virtual ALIAS example:
 153 separate domains, UNIX system accounts</a></h2>
 154
 155 <p> With the approach described in this section, every <a href="VIRTUAL_README.html#canonical">hosted domain</a>
 156 can have its own info etc. email address.  However, it still uses
 157 UNIX system accounts for local mailbox deliveries. </p>
 158
 159 <p> With <a href="ADDRESS_CLASS_README.html#virtual_alias_class">virtual alias domains</a>, each hosted address is aliased to
 160 a local UNIX system account or to a remote address.  The example
 161 below shows how to use this mechanism for the example.com domain.
 162 </p>
 163
 164 <blockquote>
 165 <pre>
 166  1 /etc/postfix/<a href="postconf.5.html">main.cf</a>:
 167  2     <a href="postconf.5.html#virtual_alias_domains">virtual_alias_domains</a> = example.com ...other <a href="VIRTUAL_README.html#canonical">hosted domains</a>...
 168  3     <a href="postconf.5.html#virtual_alias_maps">virtual_alias_maps</a> = hash:/etc/postfix/virtual
 169  4
 170  5 /etc/postfix/virtual:
 171  6     postmaster@example.com postmaster
 172  7     info@example.com       joe
 173  8     sales@example.com      jane
 174  9     # Uncomment entry below to implement a catch-all address
 175 10     # @example.com         jim
 176 11     ...virtual aliases for more domains...
 177 </pre>
 178 </blockquote>
 179
 180 <p> Notes: </p>
 181
 182 <ul>
 183
 184 <li> <p> Line 2: the <a href="postconf.5.html#virtual_alias_domains">virtual_alias_domains</a> setting tells Postfix
 185 that example.com is a so-called <a href="ADDRESS_CLASS_README.html#virtual_alias_class">virtual alias domain</a>. If you omit
 186 this setting then Postfix will reject mail (relay access denied)
 187 or will not be able to deliver it (mail for example.com loops back
 188 to myself).  </p>
 189
 190 <p> NEVER list a <a href="ADDRESS_CLASS_README.html#virtual_alias_class">virtual alias domain</a> name as a <a href="postconf.5.html#mydestination">mydestination</a>
 191 domain! </p>
 192
 193 <li> <p> Lines 3-8: the /etc/postfix/virtual file contains the virtual
 194 aliases. With the example above, mail for postmaster@example.com
 195 goes to the local postmaster, while mail for info@example.com goes
 196 to the UNIX account joe, and mail for sales@example.com goes to
 197 the UNIX account jane.  Mail for all other addresses in example.com
 198 is rejected with the error message "User unknown". </p>
 199
 200 <li> <p> Line 10: the commented out entry (text after #) shows how
 201 one would implement a catch-all virtual alias that receives mail
 202 for every example.com address not listed in the virtual alias file.
 203 This is not without risk.  Spammers nowadays try to send mail from
 204 (or mail to) every possible name that they can think of. A catch-all
 205 mailbox is likely to receive many spam messages, and many bounces
 206 for spam messages that were sent in the name of anything@example.com.
 207 </p>
 208
 209 </ul>
 210
 211 <p>Execute the command "<b>postmap /etc/postfix/virtual</b>" after
 212 changing the virtual file, and execute the command "<b>postfix
 213 reload</b>" after changing the <a href="postconf.5.html">main.cf</a> file. </p>
 214
 215 <p> Note: virtual aliases can resolve to a local address or to a
 216 remote address, or both.  They don't have to resolve to UNIX system
 217 accounts on your machine. </p>
 218
 219 <p> More details about the virtual alias file are given in the
 220 <a href="virtual.5.html">virtual(5)</a> manual page, including multiple addresses on the right-hand
 221 side. </p>
 222
 223 <p> Virtual aliasing solves one problem: it allows each domain to
 224 have its own info mail address. But there still is one drawback:
 225 each virtual address is aliased to a UNIX system account. As you
 226 add more virtual addresses you also add more UNIX system accounts.
 227 The next section eliminates this problem. </p>
 228
 229 <h2><a name="virtual_mailbox">Postfix virtual MAILBOX example:
 230 separate domains, non-UNIX accounts</a></h2>
 231
 232 <p> As a system hosts more and more domains and users, it becomes less
 233 desirable to give every user their own UNIX system account.</p>
 234
 235 <p> With the Postfix <a href="virtual.8.html">virtual(8)</a> mailbox delivery agent, every
 236 recipient address can have its own virtual mailbox. Unlike virtual
 237 alias domains, <a href="ADDRESS_CLASS_README.html#virtual_mailbox_class">virtual mailbox domains</a> do not need the clumsy
 238 translation from each recipient addresses into a different address,
 239 and owners of a virtual mailbox address do not need to have a UNIX
 240 system account.</p>
 241
 242 <p> The Postfix <a href="virtual.8.html">virtual(8)</a> mailbox delivery agent looks up the user
 243 mailbox pathname, uid and gid via separate tables that are searched
 244 with the recipient's mail address. Maildir style delivery is turned
 245 on by terminating the mailbox pathname with "/".</p>
 246
 247 <p> If you find the idea of multiple tables bothersome, remember
 248 that you can migrate the information (once it works), to an SQL
 249 database.  If you take that route, be sure to review the <a
 250 href="#local_vs_database"> "local files versus databases"</a>
 251 section at the top of this document.</p>
 252
 253 <p> Here is an example of a <a href="ADDRESS_CLASS_README.html#virtual_mailbox_class">virtual mailbox domain</a> "example.com":
 254 </p>
 255
 256 <blockquote>
 257 <pre>
 258  1 /etc/postfix/<a href="postconf.5.html">main.cf</a>:
 259  2     <a href="postconf.5.html#virtual_mailbox_domains">virtual_mailbox_domains</a> = example.com ...more domains...
 260  3     <a href="postconf.5.html#virtual_mailbox_base">virtual_mailbox_base</a> = /var/mail/vhosts
 261  4     <a href="postconf.5.html#virtual_mailbox_maps">virtual_mailbox_maps</a> = hash:/etc/postfix/vmailbox
 262  5     <a href="postconf.5.html#virtual_minimum_uid">virtual_minimum_uid</a> = 100
 263  6     <a href="postconf.5.html#virtual_uid_maps">virtual_uid_maps</a> = static:5000
 264  7     <a href="postconf.5.html#virtual_gid_maps">virtual_gid_maps</a> = static:5000
 265  8     <a href="postconf.5.html#virtual_alias_maps">virtual_alias_maps</a> = hash:/etc/postfix/virtual
 266  9
 267 10 /etc/postfix/vmailbox:
 268 11     info@example.com    example.com/info
 269 12     sales@example.com   example.com/sales/
 270 13     # Comment out the entry below to implement a catch-all.
 271 14     # @example.com      example.com/catchall
 272 15     ...virtual mailboxes for more domains...
 273 16
 274 17 /etc/postfix/virtual:
 275 18     postmaster@example.com postmaster
 276 </pre>
 277 </blockquote>
 278
 279 <p> Notes: </p>
 280
 281 <ul>
 282
 283 <li> <p> Line 2: The <a href="postconf.5.html#virtual_mailbox_domains">virtual_mailbox_domains</a> setting tells Postfix
 284 that example.com is a so-called <a href="ADDRESS_CLASS_README.html#virtual_mailbox_class">virtual mailbox domain</a>. If you omit
 285 this setting then Postfix will reject mail (relay access denied)
 286 or will not be able to deliver it (mail for example.com loops back
 287 to myself).  </p>
 288
 289 <p> NEVER list a <a href="ADDRESS_CLASS_README.html#virtual_mailbox_class">virtual MAILBOX domain</a> name as a <a href="postconf.5.html#mydestination">mydestination</a>
 290 domain! </p>
 291
 292 <p> NEVER list a <a href="ADDRESS_CLASS_README.html#virtual_mailbox_class">virtual MAILBOX domain</a> name as a virtual ALIAS
 293 domain! </p>
 294
 295 <li> <p> Line 3: The <a href="postconf.5.html#virtual_mailbox_base">virtual_mailbox_base</a> parameter specifies a
 296 prefix for all virtual mailbox pathnames. This is a safety mechanism
 297 in case someone makes a mistake. It prevents mail from being
 298 delivered all over the file system. </p>
 299
 300 <li> <p> Lines 4, 10-15: The <a href="postconf.5.html#virtual_mailbox_maps">virtual_mailbox_maps</a> parameter specifies
 301 the lookup table with mailbox (or maildir) pathnames, indexed by
 302 the virtual mail address.  In this example, mail for info@example.com
 303 goes to the mailbox at /var/mail/vhosts/example.com/info while mail
 304 for sales@example.com goes to the maildir located at
 305 /var/mail/vhosts/example.com/sales/. </p>
 306
 307 <li> <p> Line 5: The <a href="postconf.5.html#virtual_minimum_uid">virtual_minimum_uid</a> specifies a lower bound
 308 on the mailbox or maildir owner's UID.  This is a safety mechanism
 309 in case someone makes a mistake. It prevents mail from being written
 310 to sensitive files. </p>
 311
 312 <li> <p> Lines 6, 7: The <a href="postconf.5.html#virtual_uid_maps">virtual_uid_maps</a> and <a href="postconf.5.html#virtual_gid_maps">virtual_gid_maps</a>
 313 parameters specify that all the virtual mailboxes are owned by a
 314 fixed uid and gid 5000.  If this is not what you want, specify
 315 lookup tables that are searched by the recipient's mail address.
 316 </p>
 317
 318 <li> <p> Line 14: The commented out entry (text after #) shows how
 319 one would implement a catch-all virtual mailbox address. Be prepared
 320 to receive a lot of spam, as well as bounced spam that was sent in
 321 the name of anything@example.com. </p>
 322
 323 <p> NEVER put a virtual MAILBOX wild-card in the virtual ALIAS
 324 file!! </p>
 325
 326 <li> <p> Lines 8, 17, 18: As you see, it is possible to mix virtual
 327 aliases with virtual mailboxes. We use this feature to redirect
 328 mail for example.com's postmaster address to the local postmaster.
 329 You can use the same mechanism to redirect an address to a remote
 330 address.  </p>
 331
 332 <li> <p> Line 18: This example assumes that in <a href="postconf.5.html">main.cf</a>, $<a href="postconf.5.html#myorigin">myorigin</a>
 333 is listed under the <a href="postconf.5.html#mydestination">mydestination</a> parameter setting.  If that is
 334 not the case, specify an explicit domain name on the right-hand
 335 side of the virtual alias table entries or else mail will go to
 336 the wrong domain. </p>
 337
 338 </ul>
 339
 340 <p> Execute the command "<b>postmap /etc/postfix/virtual</b>" after
 341 changing the virtual file, execute "<b>postmap /etc/postfix/vmailbox</b>"
 342 after changing the vmailbox file, and execute the command "<b>postfix
 343 reload</b>" after changing the <a href="postconf.5.html">main.cf</a> file. </p>
 344
 345 <p> Note: mail delivery happens with the recipient's UID/GID
 346 privileges specified with <a href="postconf.5.html#virtual_uid_maps">virtual_uid_maps</a> and <a href="postconf.5.html#virtual_gid_maps">virtual_gid_maps</a>.
 347 Postfix 2.0 and earlier will not create mailDIRs in world-writable
 348 parent directories; you must create them in advance before you can
 349 use them. Postfix may be able to create mailBOX files by itself,
 350 depending on parent directory write permissions, but it is safer
 351 to create mailBOX files ahead of time. </p>
 352
 353 <p> More details about the virtual mailbox delivery agent are given
 354 in the <a href="virtual.8.html">virtual(8)</a> manual page. </p>
 355
 356 <h2><a name="in_virtual_other">Non-Postfix mailbox store: separate
 357 domains, non-UNIX accounts</a></h2>
 358
 359 <p> This is a variation on the Postfix <a href="VIRTUAL_README.html#virtual_mailbox">virtual mailbox example</a>.
 360 Again, every hosted address can have its own mailbox.  </p>
 361
 362 <p> While non-Postfix software is being used for final delivery,
 363 some Postfix concepts are still needed in order to glue everything
 364 together.  For additional background on this glue you may want to
 365 take a look at the <a href="ADDRESS_CLASS_README.html#virtual_mailbox_class">virtual mailbox domain</a> class as defined in the
 366 <a href="ADDRESS_CLASS_README.html">ADDRESS_CLASS_README</a> file. </p>
 367
 368 <p> The text in this section describes what things should look like
 369 from Postfix's point of view. See <a href="CYRUS_README.html">CYRUS_README</a> or <a href="MAILDROP_README.html">MAILDROP_README</a>
 370 for specific information about Cyrus or about Courier maildrop.
 371 </p>
 372
 373 <p> Here is an example for a <a href="VIRTUAL_README.html#canonical">hosted domain</a> example.com that delivers
 374 to a non-Postfix delivery agent: </p>
 375
 376 <blockquote>
 377 <pre>
 378  1 /etc/postfix/<a href="postconf.5.html">main.cf</a>:
 379  2     <a href="postconf.5.html#virtual_transport">virtual_transport</a> = ...see below...
 380  3     <a href="postconf.5.html#virtual_mailbox_domains">virtual_mailbox_domains</a> = example.com ...more domains...
 381  4     <a href="postconf.5.html#virtual_mailbox_maps">virtual_mailbox_maps</a> = hash:/etc/postfix/vmailbox
 382  5     <a href="postconf.5.html#virtual_alias_maps">virtual_alias_maps</a> = hash:/etc/postfix/virtual
 383  6
 384  7 /etc/postfix/vmailbox:
 385  8     info@example.com    whatever
 386  9     sales@example.com   whatever
 387 10     # Comment out the entry below to implement a catch-all.
 388 11     # Configure the mailbox store to accept all addresses.
 389 12     # @example.com      whatever
 390 13     ...virtual mailboxes for more domains...
 391 14
 392 15 /etc/postfix/virtual:
 393 16     postmaster@example.com postmaster
 394 </pre>
 395 </blockquote>
 396
 397 <p> Notes: </p>
 398
 399 <ul>
 400
 401 <li> <p> Line 2: With delivery to a non-Postfix mailbox store for
 402 <a href="VIRTUAL_README.html#canonical">hosted domains</a>, the <a href="postconf.5.html#virtual_transport">virtual_transport</a> parameter usually specifies
 403 the Postfix LMTP client, or the name of a <a href="master.5.html">master.cf</a> entry that
 404 executes non-Postfix software via the pipe delivery agent.  Typical
 405 examples (use only one): </p>
 406
 407 <blockquote>
 408 <pre>
 409 <a href="postconf.5.html#virtual_transport">virtual_transport</a> = <a href="lmtp.8.html">lmtp</a>:unix:/path/name (uses UNIX-domain socket)
 410 <a href="postconf.5.html#virtual_transport">virtual_transport</a> = <a href="lmtp.8.html">lmtp</a>:hostname:port   (uses TCP socket)
 411 <a href="postconf.5.html#virtual_transport">virtual_transport</a> = maildrop:            (uses <a href="pipe.8.html">pipe(8)</a> to command)
 412 </pre>
 413 </blockquote>
 414
 415 <p> Postfix comes ready with support for LMTP.  And an example
 416 maildrop delivery method is already defined in the default Postfix
 417 <a href="master.5.html">master.cf</a> file. See the <a href="MAILDROP_README.html">MAILDROP_README</a> document for more details.
 418 </p>
 419
 420 <li> <p> Line 3: The <a href="postconf.5.html#virtual_mailbox_domains">virtual_mailbox_domains</a> setting tells Postfix
 421 that example.com is delivered via the <a href="postconf.5.html#virtual_transport">virtual_transport</a> that was
 422 discussed in the previous paragraph. If you omit this
 423 <a href="postconf.5.html#virtual_mailbox_domains">virtual_mailbox_domains</a> setting then Postfix will either reject
 424 mail (relay access denied) or will not be able to deliver it (mail
 425 for example.com loops back to myself). </p>
 426
 427 <p> NEVER list a <a href="ADDRESS_CLASS_README.html#virtual_mailbox_class">virtual MAILBOX domain</a> name as a <a href="postconf.5.html#mydestination">mydestination</a>
 428 domain!  </p>
 429
 430 <p> NEVER list a <a href="ADDRESS_CLASS_README.html#virtual_mailbox_class">virtual MAILBOX domain</a> name as a virtual ALIAS
 431 domain!  </p>
 432
 433 <li> <p> Lines 4, 7-13: The <a href="postconf.5.html#virtual_mailbox_maps">virtual_mailbox_maps</a> parameter specifies
 434 the lookup table with all valid recipient addresses. The lookup
 435 result value is ignored by Postfix.  In the above example,
 436 info@example.com
 437 and sales@example.com are listed as valid addresses; other mail for
 438 example.com is rejected with "User unknown" by the Postfix SMTP
 439 server. It's left up to the non-Postfix delivery agent to reject
 440 non-existent recipients from local submission or from local alias
 441 expansion.  If you intend to
 442 use LDAP, MySQL or PgSQL instead of local files, be sure to review
 443 the <a href="#local_vs_database"> "local files versus databases"</a>
 444 section at the top of this document! </p>
 445
 446 <li> <p> Line 12: The commented out entry (text after #) shows how
 447 one would inform Postfix of the existence of a catch-all address.
 448 Again, the lookup result is ignored by Postfix. </p>
 449
 450 <p> NEVER put a virtual MAILBOX wild-card in the virtual ALIAS
 451 file!! </p>
 452
 453 <p> Note: if you specify a wildcard in <a href="postconf.5.html#virtual_mailbox_maps">virtual_mailbox_maps</a>, then
 454 you still need to configure the non-Postfix mailbox store to receive
 455 mail for any address in that domain. </p>
 456
 457 <li> <p> Lines 5, 15, 16: As you see above, it is possible to mix
 458 virtual aliases with virtual mailboxes. We use this feature to
 459 redirect mail for example.com's postmaster address to the local
 460 postmaster. You can use the same mechanism to redirect any addresses
 461 to a local or remote address.  </p>
 462
 463 <li> <p> Line 16: This example assumes that in <a href="postconf.5.html">main.cf</a>, $<a href="postconf.5.html#myorigin">myorigin</a>
 464 is listed under the <a href="postconf.5.html#mydestination">mydestination</a> parameter setting.  If that is
 465 not the case, specify an explicit domain name on the right-hand
 466 side of the virtual alias table entries or else mail will go to
 467 the wrong domain. </p>
 468
 469 </ul>
 470
 471 <p> Execute the command "<b>postmap /etc/postfix/virtual</b>" after
 472 changing the virtual file, execute "<b>postmap /etc/postfix/vmailbox</b>"
 473 after changing the vmailbox file, and execute the command "<b>postfix
 474 reload</b>" after changing the <a href="postconf.5.html">main.cf</a> file. </p>
 475
 476 <h2><a name="forwarding">Mail forwarding domains</a></h2>
 477
 478 <p> Some providers host domains that have no (or only a few) local
 479 mailboxes. The main purpose of these domains is to forward mail
 480 elsewhere.  The following example shows how to set up example.com
 481 as a mail forwarding domain: </p>
 482
 483 <blockquote>
 484 <pre>
 485  1 /etc/postfix/<a href="postconf.5.html">main.cf</a>:
 486  2     <a href="postconf.5.html#virtual_alias_domains">virtual_alias_domains</a> = example.com ...other <a href="VIRTUAL_README.html#canonical">hosted domains</a>...
 487  3     <a href="postconf.5.html#virtual_alias_maps">virtual_alias_maps</a> = hash:/etc/postfix/virtual
 488  4
 489  5 /etc/postfix/virtual:
 490  6     postmaster@example.com postmaster
 491  7     joe@example.com        joe@somewhere
 492  8     jane@example.com       jane@somewhere-else
 493  9     # Uncomment entry below to implement a catch-all address
 494 10     # @example.com         jim@yet-another-site
 495 11     ...virtual aliases for more domains...
 496 </pre>
 497 </blockquote>
 498
 499 <p> Notes: </p>
 500
 501 <ul>
 502
 503 <li> <p> Line 2: The <a href="postconf.5.html#virtual_alias_domains">virtual_alias_domains</a> setting tells Postfix
 504 that example.com is a so-called <a href="ADDRESS_CLASS_README.html#virtual_alias_class">virtual alias domain</a>. If you omit
 505 this setting then Postfix will reject mail (relay access denied)
 506 or will not be able to deliver it (mail for example.com loops back
 507 to myself). </p>
 508
 509 <p> NEVER list a <a href="ADDRESS_CLASS_README.html#virtual_alias_class">virtual alias domain</a> name as a <a href="postconf.5.html#mydestination">mydestination</a>
 510 domain! </p>
 511
 512 <li> <p> Lines 3-11: The /etc/postfix/virtual file contains the
 513 virtual aliases.  With the example above, mail for postmaster@example.com
 514 goes to the local postmaster, while mail for joe@example.com goes
 515 to the remote address joe@somewhere, and mail for jane@example.com
 516 goes to the remote address jane@somewhere-else.  Mail for all other
 517 addresses in example.com is rejected with the error message "User
 518 unknown". </p>
 519
 520 <li> <p> Line 10: The commented out entry (text after #) shows how
 521 one would implement a catch-all virtual alias that receives mail
 522 for every example.com address not listed in the virtual alias file.
 523 This is not without risk.  Spammers nowadays try to send mail from
 524 (or mail to) every possible name that they can think of. A catch-all
 525 mailbox is likely to receive many spam messages, and many bounces
 526 for spam messages that were sent in the name of anything@example.com.
 527 </p>
 528
 529 </ul>
 530
 531 <p> Execute the command "<b>postmap /etc/postfix/virtual</b>" after
 532 changing the virtual file, and execute the command "<b>postfix
 533 reload</b>" after changing the <a href="postconf.5.html">main.cf</a> file. </p>
 534
 535 <p> More details about the virtual alias file are given in the
 536 <a href="virtual.5.html">virtual(5)</a> manual page, including multiple addresses on the right-hand
 537 side. </p>
 538
 539 <h2><a name="mailing_lists">Mailing lists</a></h2>
 540
 541 <p> The examples that were given above already show how to direct
 542 mail for virtual postmaster addresses to a local postmaster. You
 543 can use the same method to direct mail for any address to a local
 544 or remote address. </p>
 545
 546 <p> There is one major limitation:  virtual aliases and virtual
 547 mailboxes can't directly deliver to mailing list managers such as
 548 majordomo.  The solution is to set up virtual aliases that direct
 549 virtual addresses to the local delivery agent: </p>
 550
 551 <blockquote>
 552 <pre>
 553 /etc/postfix/<a href="postconf.5.html">main.cf</a>:
 554     <a href="postconf.5.html#virtual_alias_maps">virtual_alias_maps</a> = hash:/etc/postfix/virtual
 555
 556 /etc/postfix/virtual:
 557     listname-request@example.com listname-request
 558     listname@example.com         listname
 559     owner-listname@example.com   owner-listname
 560
 561 /etc/aliases:
 562     listname: "|/some/where/majordomo/wrapper ..."
 563     owner-listname: ...
 564     listname-request: ...
 565 </pre>
 566 </blockquote>
 567
 568 <p> This example assumes that in <a href="postconf.5.html">main.cf</a>, $<a href="postconf.5.html#myorigin">myorigin</a> is listed under
 569 the <a href="postconf.5.html#mydestination">mydestination</a> parameter setting.  If that is not the case,
 570 specify an explicit domain name on the right-hand side of the
 571 virtual alias table entries or else mail will go to the wrong
 572 domain. </p>
 573
 574 <p> More information about the Postfix local delivery agent can be
 575 found in the <a href="local.8.html">local(8)</a> manual page. </p>
 576
 577 <p> Why does this example use a clumsy virtual alias instead of a
 578 more elegant transport mapping? The reason is that mail for the
 579 virtual mailing list would be rejected with "User unknown".  In
 580 order to make the transport mapping work one would still need a
 581 bunch of virtual alias or virtual mailbox table entries. </p>
 582
 583 <ul>
 584
 585 <li> In case of a <a href="ADDRESS_CLASS_README.html#virtual_alias_class">virtual alias domain</a>, there would need to be one
 586 identity mapping from each mailing list address to itself.
 587
 588 <li> In case of a <a href="ADDRESS_CLASS_README.html#virtual_mailbox_class">virtual mailbox domain</a>, there would need to be
 589 a dummy mailbox for each mailing list address.
 590
 591 </ul>
 592
 593 <h2><a name="autoreplies">Autoreplies</a></h2>
 594
 595 <p> In order to set up an autoreply for virtual recipients while
 596 still delivering mail as normal, set up a rule in a virtual alias
 597 table: </p>
 598
 599 <blockquote>
 600 <pre>
 601 /etc/postfix/<a href="postconf.5.html">main.cf</a>:
 602     <a href="postconf.5.html#virtual_alias_maps">virtual_alias_maps</a> = hash:/etc/postfix/virtual
 603
 604 /etc/postfix/virtual:
 605     user@domain.tld user@domain.tld, user@domain.tld@autoreply.<a href="postconf.5.html#mydomain">mydomain</a>.tld
 606 </pre>
 607 </blockquote>
 608
 609 <p> This delivers mail to the recipient, and sends a copy of the
 610 mail to the address that produces automatic replies. The address
 611 can be serviced on a different machine, or it can be serviced
 612 locally by setting up a transport map entry that pipes all mail
 613 for autoreply.<a href="postconf.5.html#mydomain">mydomain</a>.tld into some script that sends an automatic
 614 reply back to the sender. </p>
 615
 616 <p> DO NOT list autoreply.<a href="postconf.5.html#mydomain">mydomain</a>.tld in <a href="postconf.5.html#mydestination">mydestination</a>! </p>
 617
 618 <blockquote>
 619 <pre>
 620 /etc/postfix/<a href="postconf.5.html">main.cf</a>:
 621     <a href="postconf.5.html#transport_maps">transport_maps</a> = hash:/etc/postfix/transport
 622
 623 /etc/postfix/transport:
 624     autoreply.<a href="postconf.5.html#mydomain">mydomain</a>.tld  autoreply:
 625
 626 /etc/postfix/<a href="master.5.html">master.cf</a>:
 627     # =============================================================
 628     # service type  private unpriv  chroot  wakeup  maxproc command
 629     #               (yes)   (yes)   (yes)   (never) (100)
 630     # =============================================================
 631     autoreply unix  -       n       n       -       -       pipe
 632         flags= user=nobody argv=/path/to/autoreply $sender $mailbox
 633 </pre>
 634 </blockquote>
 635
 636 <p> This invokes /path/to/autoreply with the sender address and
 637 the user@domain.tld recipient address on the command line. </p>
 638
 639 <p> For more information, see the <a href="pipe.8.html">pipe(8)</a> manual page, and the
 640 comments in the Postfix <a href="master.5.html">master.cf</a> file. </p>
 641
 642 </body>
 643
 644 </html>