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diff --git a/proto/VERP_README.html b/proto/VERP_README.html new file mode 100644 index 0000000..e442c89 --- /dev/null +++ b/proto/VERP_README.html @@ -0,0 +1,289 @@ +<!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=utf-8"> + +</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 http://cr.yp.to/proto/verp.txt 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> default_verp_delimiters (default value: +=) + + <dd> <p> What VERP delimiter characters Postfix uses when VERP + style delivery is requested but no explicit delimiters are + specified. </p> + +<dt> verp_delimiter_filter (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> smtpd_authorized_verp_clients (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 + authorized_verp_clients (default: $mynetworks). </p> </dd> + +<dt> disable_verp_bounces (default: no) + + <dd> <p> Send one bounce report for multi-recipient VERP mail, + instead of 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> + +<p> Postfix 2.3 and later: </p> + +<blockquote> +<pre> +% sendmail -XV -f owner-listname other-arguments... + +% sendmail -XV+= -f owner-listname other-arguments... +</pre> +</blockquote> + +<p> Postfix 2.2 and earlier (Postfix 2.3 understands the old syntax +for backwards compatibility, but will log a warning that reminds +you of the new syntax): </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: + recipient_delimiter = + + forward_path = $home/.forward${recipient_delimiter}${extension}, + $home/.forward + propagate_unmatched_extensions = 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> + +<p> You can use the smtpd_command_filter feature to append XVERP +to SMTP commands from legacy software. This requires Postfix 2.7 +or later. </p> + +<blockquote> +<pre> +/etc/postfix/main.cf: + smtpd_command_filter = pcre:/etc/postfix/append_verp.pcre + smtpd_authorized_verp_clients = $mynetworks + +/etc/postfix/append_verp.pcre: + /^(MAIL FROM:<listname@example\.com>.*)/ $1 XVERP +</pre> +</blockquote> + +<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> + +<p> Postfix 2.3 and later:</p> +<blockquote> +<pre> +% sendmail -XV -f owner-listname .... + +% sendmail -XV+= -f owner-listname .... +</pre> +</blockquote> + +<p> Postfix 2.2 and earlier (Postfix 2.3 understands the old syntax +for backwards compatibility, but will log a warning that reminds +you of the new syntax): </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 verp_delimiter_filter +parameter. In particular, the "=" delimiter is required for qmail +compatibility (see the qmail addresses(5) manual page for details). + +</body> + +</html> |