[TriLUG] backup email server

[Tanner Lovelace]

Michael Hrivnak said the following on 6/20/04 12:00 AM:


> mydomain = hrivnak.org
> mydestination = $myhostname, localhost.$mydomain, localhost
> relay_domains = $mydestination hrivnak.org
> delay_warning_time = 24
> 
> The rest are defaults.  I think this will make the machine relay mail to 
> hrivnak.org.  Am I correct?

Not necessarily.  There is one thing missing here.  You haven't
shown us what you've setup in DNS for MX records.  Also, what
are the hostnames of the two machines?

Let's say for example, the main mail server is called mail.hrivnak.org
and the backup is mail2.hrivnak.org.  You would need something like the
following MX records in DNS for this to work correctly:

;
; MX Records
;
hrivnak.org.      2H IN MX     20 mail2.hrivnak.org.
hrivnak.org.      2H IN MX     0  mail.hrivnak.org.

What this says is that you prefer mail to go to mail.hrivnak.org
(smaller numbers mean the mail server is more preferred), but
that when it's not available, go to mail2.hrivnak.org.

Now, the other wrinkle here is that if the second mail server
for some reason thinks its the final destination for hrivnak.org
it will try to deliver the items locally.  I've only ever used
backup mail servers in other domains, so I'm not sure what
switches to use to make sure it doesn't keep any mail locally
that should be sent on.  Perhaps someone else can speak to that?

Cheers,
Tanner