File: //usr/share/webmin/postfix/help/opt_recipient_delimiter.html
<header>Separator between user names and address extensions</header>
<center><tt>recipient_delimiter</tt></center>
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This parameter specifies the separator between user names and address
extensions (<tt>user+foo</tt>). See <a href=canonical>Canonical Mapping</a>,
<a href=relocated>Relocated Mapping</a>, <a href=virtual>Virtual Domains</a>
and local(8) for the effects this has on aliases, canonical, virtual,
relocated and <tt>.forward</tt> file lookups. Basically, the software tries
<tt>user+foo</tt> and <tt>.forward+foo</tt> before trying <tt>user</tt> and
<tt>.forward</tt>.
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