[cobalt-users] Sendmail Fallback MX (was: How can I forward all mail for a domain to another mail server)

[SM <nntp@xxxxxxxxx>]

At 12:17 15-08-2001 +0100, Clive Harper wrote:
>They are constantly reporting that they are losing mail from
>their server, either due to network problems or the mail
>server itself, anyway they have asked if we could act as a
>mail host for them and provide a cache of recent mails just
>in case some go missing at their mail server.

One of the often overlooked features of Sendmail (and other MTAs) is the
Fallback MX.  This is done by adding a MX record for an offsite host which
can receive mail for your site when your site is unavailable.  If the
offsite host is unreliable you might lose mail.

You need to add an additional MX record with a higher weight to your DNS
entry for that domain and point it to the offite host.  On the offsite
host, add your domain name in the /etc/mail/relay-domains file.  You will
also have to create an mailertable entry and and have it point to your site
to avoid a MX loop on the offsite host.

>Secondly how can I keep a copy of all the mails sent to this
>domain for appx 7 days before deleting them?

Sendmail will keep the mails for 5 days before deleting them.  You can
modify that setting (O Timeout.queuereturn=7d) in the sendmail.cf.

Regards,
-sm