Hello Roger,
We don't provide a backup/fail-over SMTP server at the moment, but we'd think of providing such a feature/service shortly..
According to RFC2821, the lowest-numbered records are the most preferred, the lower the priority, the higher the preference to that mail server. Hence you can setup a new MX record with the priority of 0 (zero) & point that to your mail server (Exchange 2007).
The final DNS zone records would look like:
Quote:
mydomain.co.uk. IN A xxx.xxx.xxx.xxx ; This is the A record of the domain, which doesn't need to be changed.
mydomain.co.uk. IN MX 0 exch.mydomain.co.uk. ; Your local Exchange server's MX record with lowest priority.
mydomain.co.uk. IN MX 10 mail.mydomain.co.uk. ; Our shared server's MX record with the next priority.
mydomain.co.uk. IN MX 20 exch2.mydomain.co.uk. ; Any other exchange mail server's MX record with next higher priority.
mail. IN A xxx.xxx.xxx.xxx ; Our shared server's IP.
exch. IN A yyy.yyy.yyy.yyy ; Your local Exchange mail server's IP.
exch2. IN A zzz.zzz.zzz.zzz ; Any other exchange mail server's IP.
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Here email would flow in the direction from the lowest priority to the higher ones [only in terms of their failure].
Mail servers located globally, would query the DNS servers & will by default use the lowest priority records, here exch.mydomain.co.uk would take the lead & do all the mail transactions, while the other 2 would stay calm..
But when exch.mydomain.co.uk [your local mail server] fails, is unreachable for any reasons, the next higher priority mail server [mail.mydomain.co.uk] would kick in, here being our shared server's mail server.
If both of these above mail servers [your local & our shared] are unreachable or down & you've configured a 3rd MX, in this case [exch2.mydomain.co.uk], this mail server would then take charge of the mail transactions.
More info on MX records can be found here :
MX record - Wikipedia, the free encyclopedia
Please let us know if you have any further questions
