I used a setup like this, to sync mail between 3 different
datacenters, in a multimaster setup.
For this I used unison, running every 28seconds. And it worked well
for two years, before I changed to a better approach. Older versions
of dovecot didn't like the moves very much (pre 1.0), but when I
upgraded it to 1.0.x versions, it seemed to be happy. I discontinued
it before 1.1 was out.
Quoting Bryan Vyhmeister dovecot@bsdjournal.net:
I have an idea for running a pair of redundant dovecot mail servers that may be odd but it might work. I'm interested in any thoughts on the topic.
Would it work to run 'dsync mirror' every minute against either mdbox or sdbox mailbox on a dedicated network connection between two (or potentially three or four) mail servers? I'm trying to avoid using a NAS/SAN or some other dedicated NFS server in a simple environment with a limited number of users. Everything else about the systems could be identical. Both could receive mail using Postfix with dovecot LDA. Thank you.
Bryan