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Rossino
Asked: 2020-12-15 04:03:36 +0800 CST

smtproutes relay all except local virtual domains

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I'm using smtproutes to deliver users' email to certain domains through an external SMTP server with example.com:externalsmtp.com

How can I deliver all the emails to my external SMTP except for local virtual domains?

smtp qmail

1 Answers

  1. See the manpage qmail-remote(8), Control Files:

    smtproutes

    Artificial SMTP routes. Each route has the form domain:relay, without any extra spaces. If domain matches host, qmail-remote will connect to relay, as if host had relay as its only MX. (It will also avoid doing any CNAME lookups on recip.) host may include a colon and a port number to use instead of the normal SMTP port, 25:

    inside.af.mil:firewall.af.mil:26

    relay may be empty; this tells qmail-remote to look up MX records as usual. smtproutes may include wildcards:

    .af.mil:
:heaven.af.mil

    Here any address ending with .af.mil (but not af.mil itself) is routed by its MX records; any other address is artificially routed to heaven.af.mil.

    This doesn't state it directly, but the domain can be empty, too, which works as a wildcard. Therefore, you can specify a smart host relay, as explained e.g. by Dave Sill in Life with qmail: 3.2.4. Relaying to a smart host.

    echo ":smtp.example.com" > /var/qmail/control/smtproutes

    So, if you would like to relay everything but example.net and example.org through the smart host:

    example.net:
example.org:mail.example.org
:smtp.example.com

    Here,

    • mail to example.net will look for the MX records (empty `relay´),
    • mail to example.org will go through mail.example.org, and
    • everything else will go through the smart host smtp.example.com (empty i.e. wildcard domain).
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