[Mimedefang] Check if smtp server is alive

Bob Covell bcovell at rolet.com
Thu Nov 30 17:38:13 EST 2006


----Question----
What would be the best way to verify that the target mail server is alive
and if not re-route it to a "backup" mail server?

----Scenario----
We have front-end "filter" servers (or relay servers) that provide
MD/SA/Clam/etc.  The goal is to identify that a back-end server has gone
down and re-route the mail to a backup mail server.

To support "md_check_against_smtp_server" we have a database keyed by domain
that identifies which back-end server to validate the user on.  Using this
same database would check that server.

We could either modify our filter to check if the server is alive everytime
(expensive???) or have a daemon/cronjob run every minute/5 to populate
another database with server status.

Ultimately we would like something similar to
"md_check_against_smtp_server", maybe "md_check_smtp_server".  If this
returned "false" we would change the envelope to the backup.

Also, we are NOT wanting to perform the backup via dns.  We could have
another MX with a higher weight but our goal is to have a non-published
backup mail server.

Any ideas?

Thanks,

-Bob




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