248 lines
7.9 KiB
HTML
248 lines
7.9 KiB
HTML
<!doctype html public "-//W3C//DTD HTML 4.01 Transitional//EN"
|
|
"http://www.w3.org/TR/html4/loose.dtd">
|
|
|
|
<html>
|
|
|
|
<head>
|
|
|
|
<title>Postfix VERP Howto</title>
|
|
|
|
<meta http-equiv="Content-Type" content="text/html; charset=us-ascii">
|
|
|
|
</head>
|
|
|
|
<body>
|
|
|
|
<h1><img src="postfix-logo.jpg" width="203" height="98" ALT="">Postfix VERP Howto</h1>
|
|
|
|
<hr>
|
|
|
|
<h2>Postfix VERP support</h2>
|
|
|
|
<p> Postfix versions 1.1 and later support variable envelope return
|
|
path addresses on request. When VERP style delivery is requested,
|
|
each recipient of a message receives a customized copy of the
|
|
message, with his/her own recipient address encoded in the envelope
|
|
sender address. </p>
|
|
|
|
<p> For example, when VERP style delivery is requested, Postfix
|
|
delivers mail from "<tt>owner-listname@origin</tt>" for a recipient
|
|
"<tt>user@domain</tt>", with a sender address that encodes the
|
|
recipient as follows: </p>
|
|
|
|
<blockquote>
|
|
<pre>
|
|
owner-listname+user=domain@origin
|
|
</pre>
|
|
</blockquote>
|
|
|
|
<p> Thus, undeliverable mail can reveal the undeliverable recipient
|
|
address without requiring the list owner to parse bounce messages.
|
|
</p>
|
|
|
|
<p> The VERP concept was popularized by the qmail MTA and by the ezmlm
|
|
mailing list manager. See <a href="http://cr.yp.to/proto/verp.txt">http://cr.yp.to/proto/verp.txt</a> for the
|
|
ideas behind this concept. </p>
|
|
|
|
<p> Topics covered in this document: </p>
|
|
|
|
<ul>
|
|
|
|
<li> <a href="#config"> Postfix VERP configuration parameters </a>
|
|
|
|
<li> <a href="#majordomo"> Using VERP with majordomo etc. mailing lists </a>
|
|
|
|
<li> <a href="#smtp"> VERP support in the Postfix SMTP server</a>
|
|
|
|
<li> <a href="#sendmail"> VERP support in the Postfix sendmail command </a>
|
|
|
|
<li> <a href="#qmqp"> VERP support in the Postfix QMQP server </a>
|
|
|
|
</ul>
|
|
|
|
<h2> <a name="config"> Postfix VERP configuration parameters </a> </h2>
|
|
|
|
With Postfix, the whole process is controlled by four configuration
|
|
parameters.
|
|
|
|
<dl>
|
|
|
|
<dt> <a href="postconf.5.html#default_verp_delimiters">default_verp_delimiters</a> (default value: +=)
|
|
|
|
<dd> <p> What VERP delimiter characters Postfix uses when VERP
|
|
style delivery is requested but no explicit delimiters are
|
|
specified. </p>
|
|
|
|
<dt> <a href="postconf.5.html#verp_delimiter_filter">verp_delimiter_filter</a> (default: -+=)
|
|
|
|
<dd> <p> What characters Postfix accepts as VERP delimiter
|
|
characters on the sendmail command line and in SMTP commands.
|
|
Many characters must not be used as VERP delimiter characters,
|
|
either because they already have a special meaning in email
|
|
addresses (such as the @ or the %), because they are used as
|
|
part of a username or domain name (such as alphanumerics), or
|
|
because they are non-ASCII or control characters. And who
|
|
knows, some characters may tickle bugs in vulnerable software,
|
|
and we would not want that to happen. </p> </dd>
|
|
|
|
<dt> <a href="postconf.5.html#smtpd_authorized_verp_clients">smtpd_authorized_verp_clients</a> (default value: none)
|
|
|
|
<dd> <p> What SMTP clients are allowed to request VERP style
|
|
delivery. The Postfix QMQP server uses its own access control
|
|
mechanism, and local submission (via /usr/sbin/sendmail etc.)
|
|
is always authorized. To authorize a host, list its name, IP
|
|
address, subnet (net/mask) or parent .domain. </p>
|
|
|
|
<p> With Postfix versions 1.1 and 2.0, this parameter is called
|
|
<a href="postconf.5.html#authorized_verp_clients">authorized_verp_clients</a> (default: $<a href="postconf.5.html#mynetworks">mynetworks</a>). </p> </dd>
|
|
|
|
<dt> <a href="postconf.5.html#disable_verp_bounces">disable_verp_bounces</a> (default: no)
|
|
|
|
<dd> <p> if Postfix sends one bounce report for multi-recipient
|
|
VERP mail, or one bounce report per recipient. The default,
|
|
one per recipient, is what ezmlm needs. </p> </dd>
|
|
|
|
</dl>
|
|
|
|
<h2> <a name="majordomo"> Using VERP with majordomo etc. mailing lists </a> </h2>
|
|
|
|
<p> In order to make VERP useful with majordomo etc. mailing lists,
|
|
you would configure the list manager to submit mail according
|
|
to one of the following two forms: </p>
|
|
|
|
<blockquote>
|
|
<pre>
|
|
% sendmail -V -f owner-listname other-arguments...
|
|
|
|
% sendmail -V+= -f owner-listname other-arguments...
|
|
</pre>
|
|
</blockquote>
|
|
|
|
<p> The first form uses the default main.cf VERP delimiter characters.
|
|
The second form allows you to explicitly specify the VERP delimiter
|
|
characters. The example shows the recommended values. </p>
|
|
|
|
<p> This text assumes that you have set up an owner-listname alias
|
|
that routes undeliverable mail to a real person: </p>
|
|
|
|
<blockquote>
|
|
<pre>
|
|
/etc/aliases:
|
|
owner-listname: yourname+listname
|
|
</pre>
|
|
</blockquote>
|
|
|
|
<p> In order to process bounces we are going to make extensive use
|
|
of address extension tricks. </p>
|
|
|
|
<p> You need to tell Postfix that + is the separator between an
|
|
address and its optional address extension, that address extensions
|
|
are appended to .forward file names, and that address extensions
|
|
are to be discarded when doing alias expansions: </p>
|
|
|
|
<blockquote>
|
|
<pre>
|
|
/etc/postfix/main.cf:
|
|
<a href="postconf.5.html#recipient_delimiter">recipient_delimiter</a> = +
|
|
<a href="postconf.5.html#forward_path">forward_path</a> = $home/.forward${<a href="postconf.5.html#recipient_delimiter">recipient_delimiter</a>}${extension},
|
|
$home/.forward
|
|
<a href="postconf.5.html#propagate_unmatched_extensions">propagate_unmatched_extensions</a> = canonical, virtual
|
|
</pre>
|
|
</blockquote>
|
|
|
|
<p> (the last two parameter settings are default settings). </p>
|
|
|
|
<p> You need to set up a file named .forward+listname with the
|
|
commands that process all the mail that is sent to the owner-listname
|
|
address: </p>
|
|
|
|
<blockquote>
|
|
<pre>
|
|
~/.forward+listname:
|
|
"|/some/where/command ..."
|
|
</pre>
|
|
</blockquote>
|
|
|
|
<p> With this set up, undeliverable mail for user@domain will be returned
|
|
to the following address: </p>
|
|
|
|
<blockquote>
|
|
<pre>
|
|
owner-listname+user=domain@your.domain
|
|
</pre>
|
|
</blockquote>
|
|
|
|
<p> which is processed by the command in your .forward+listname file.
|
|
The message should contain, among others, a To: header with the
|
|
encapsulated recipient sender address: </p>
|
|
|
|
<blockquote>
|
|
<pre>
|
|
To: owner-listname+user=domain@your.domain
|
|
</pre>
|
|
</blockquote>
|
|
|
|
<p> It is left as an exercise for the reader to parse the To: header
|
|
line and to pull out the user=domain part from the recipient address.
|
|
</p>
|
|
|
|
<h2> <a name="smtp"> VERP support in the Postfix SMTP server </a> </h2>
|
|
|
|
<p> The Postfix SMTP server implements a command XVERP to enable
|
|
VERP style delivery. The syntax allows two forms: </p>
|
|
|
|
<blockquote>
|
|
<pre>
|
|
MAIL FROM:<sender@domain> XVERP
|
|
|
|
MAIL FROM:<sender@domain> XVERP=+=
|
|
</pre>
|
|
</blockquote>
|
|
|
|
<p> The first form uses the default main.cf VERP delimiters, the
|
|
second form overrides them explicitly. The values shown are the
|
|
recommended ones. </p>
|
|
|
|
<h2> <a name="sendmail"> VERP support in the Postfix sendmail command </a> </h2>
|
|
|
|
<p> The Postfix sendmail command has a -V flag to request VERP style
|
|
delivery. Specify one of the following two forms: </p>
|
|
|
|
<blockquote>
|
|
<pre>
|
|
% sendmail -V -f owner-listname ....
|
|
|
|
% sendmail -V+= -f owner-listname ....
|
|
</pre>
|
|
</blockquote>
|
|
|
|
<p> The first form uses the default main.cf VERP delimiters, the
|
|
second form overrides them explicitly. The values shown are the
|
|
recommended ones. </p>
|
|
|
|
<h2> <a name="qmqp"> VERP support in the Postfix QMQP server </a> </h2>
|
|
|
|
<p> When the Postfix QMQP server receives mail with an envelope
|
|
sender address of the form: </p>
|
|
|
|
<blockquote>
|
|
<pre>
|
|
listname-@your.domain-@[]
|
|
</pre>
|
|
</blockquote>
|
|
|
|
<p> Postfix generates sender addresses
|
|
"<tt>listname-user=domain@your.domain</tt>", using "-=" as the VERP
|
|
delimiters because qmail/ezmlm expect this. </p>
|
|
|
|
<p> More generally, a sender address of "<tt>prefix@origin-@[]</tt>"
|
|
requests VERP style delivery with sender addresses of the form
|
|
"<tt>prefixuser=domain@origin</tt>". However, Postfix allows only
|
|
VERP delimiters that are specified with the <a href="postconf.5.html#verp_delimiter_filter">verp_delimiter_filter</a>
|
|
parameter. In particular, the "=" delimiter is required for qmail
|
|
compatibility (see the qmail addresses(5) manual page for details).
|
|
|
|
</body>
|
|
|
|
</html>
|