<header>External command to use instead of mailbox delivery</header>

<center><tt>mailbox_command</tt></center>
<hr>

This parameter specifies the optional external command to use instead of mailbox
delivery. The command is run as the recipient with proper <tt>HOME</tt>,
<tt>SHELL</tt> and <tt>LOGNAME</tt> environment settings. Exception: delivery
for <tt>root</tt> is done as <tt>$default_user</tt>.

<p>

Other environment variables of interest: <tt>USER</tt> (recipient username),
<tt>EXTENSION</tt> (address extension), <tt>DOMAIN</tt> (domain part of address),
and <tt>LOCAL</tt> (the address localpart).

<p>

Unlike other Postfix configuration parameters, this
parameter is not subjected to parameter substitutions. This is to
make it easier to specify shell syntax (see example below).

<p>

Avoid shell meta characters because they will force Postfix to run
an expensive shell process. <tt>Procmail</tt> alone is expensive enough.

<p>

IF YOU USE THIS TO DELIVER MAIL SYSTEM-WIDE, YOU MUST SET UP AN
ALIAS THAT FORWARDS MAIL FOR ROOT TO A REAL USER.

<p>

Examples:
<ul>
<li><tt>/some/where/procmail</tt> 
<li><tt>/some/where/procmail -a "$EXTENSION"</tt>
</ul>

<hr>