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Redundant Mail Delivery
ivanfilippov
Member
Hi everyone!
I'm playing around with setting up a redundant mail system and was hoping someone here had some experience with exim4 and dovecot and their interoperability.
I would like to have two servers (mail1 and mail2, for the sake of the discussion) that will allow mail to continue to be accepted for a domain (example.com) if either is down. My plan so far looks like this:
- Set up MX records for mail1 and mail2
- mail1 will run exim4 and dovecot
- mail2 will run exim4
- dovecot will be the only application that will store mail, and will expose it via IMAP for clients and webmail applications
- exim4 on mail1 will contact dovecot to store received mail via LDA (ie. using dovecots deliver mechanism)
- exim4 on mail2 will contact dovecot to store received mail via an LMTP server that dovecot provides
- If mail1 goes down, then mail2 will accept incoming mail and store it in its queue until mail1 returns.
- If mail2 goes down, mail1 will continue to function normally.
Does this implementation sound sane and is this possible with the software that I've chosen? Any tips on configuring exim4 or dovecot? Aside from not making exim an open relay. 
Comments
you may change mx record of DNS?
Why do you want exim4 on mail2 to talk directly to dovecot on mail1? If you set up exim4 on mail2 up as a normal mx-backup it will forward mail to exim4 on mail1. Much less configuration needed.
@Leo That's a great set up! I got so wrapped up in getting each exim to talk to dovecot that I didn't even think of doing it this way. Thank you very much @Leo!