MX record Question

Waltner, Steve swaltner at lsil.com
Thu Aug 9 16:09:47 UTC 2001


> The question is how does this work?
> 
> MX 10 mail01.domain.com
> MX 10 mail02.domain.com
> 
> 
> If for example this in theory will round robin, what would happen if
> mail01
> were to go down, would mail02 be the next on the list even after being
> resolved?  My email admin wanted to know how this would work.  We think
> that
> it should go to the next one in line, this of course depending on the MTA.
> Could someone shed some light.
> 
> Thanks,
> 
> Mark
> 
> 
When BIND returns a response to an MX query for this domain name, it will
return the two entries ordered in round-robin fashion. So if mail01 was
listed before mail02 in the response, the remote mailserver would first
attempt to contact mail01, and then after a minute the TCP connection to
port 25 (SMTP server) would fail, so the remote server would then try mail02
and the mail would go through.

Steve




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