[plug] Sendmail as a backup MX

[ryan at is.as.geeky.as]

Dear PLUG,

Does anyone successfully have a Sendmail primary MX of one domain running as
backup MX for another domain?

There seems to be little info available about how to configure such a setup,
and what I have found I have followed to no avail.

I guess firstly, is what I just asked possible?  Or does the backup machine
bhave to be purely a backup server and not operate as a primary mail server
for any domains?

The problems I am having are either that it tries to deliver mail it has
received as a backup MX locally .. indicating I have put the backup domain
as a local domain (which I haven't), or it attempts to relay the backup mail
to itself because the primary is still down so it looks up the backup and
finds itself and complains of a mail routing loop.

I'd list what I've tried but that would be a very long email ... so if
anyone has a definitive solution that I can try and report back on, that
would be a tad better :)

Thanks,

Ryan