I’d like to build robust mail system that can withstand outages. For this purpose I rent 2 servers (lets call it mx1 and mx2) in 2 different datacenters, set up Exim on both as SMTP, and Dovecot as LDA, IMAP and POP3 server (Exim pass the message to Dovecot LDA to deliver it).
Now I’d like to sync mail storages of these servers so even if one of these servers will disappear I’ll simple change DNS for, say, mx1 to have it point to mx2 address, and all the same mailstore be available to serve messages from.
The problem is, I don’t like to rsync whole mailstorage from mx1 to mx2 and vise versa to keep mailstorages synced (it takes a lot of resources to find out only a few messages to copy over; and to keep storages as synced as I can afford I’ll have to set up cron this rsync at, say, each 5 minutes).
At the same time, I think once I saw some config for Exim or Dovecot LDA so LDA will deliver the same message to both servers. So now, please advice on how should I set up robust mail system so my users stay happy, and the solution be nice and good-engineered ) So to say, it is not necessary to use Dovecot as LDA as Exim can deliver inself, I just wanted to know how to withstand one of mx-es outage, or whole DC (one of two DCs) offline or outage.
Thank you in advance!
