New mail server setup

Matthew Seaman m.seaman at
Wed Sep 16 13:49:49 UTC 2009

Steve Bertrand wrote:

> What I don't have, and have always wondered about, is live redundancy
> for the IMAP/POP services.
> I know that this would be a challenge to some degree considering the
> high volume of data changes.
> Perhaps a carp(4) setup between a couple of MDA's, where when the
> primary is up, a constant rsync pushes the data to the backup. Or
> perhaps a combination of rsync for manual changes, and a method to have
> the primary write the emails to a local disk, and a network disk
> simultaneously?
> If anyone has a setup that has redundancy for their IMAP/POP services,
> and a method to keep the changing data relatively up-to-date, I'd love
> to hear about it.

Now, that is a different kettle of fish.  This is a job for cyrus imap.
I suggest googling for 'cyrus murder' -- this is almost, but not quite,
a fully resilient mail store / IMAP system.  Your mail store is divided
into frontend IMAP protocol servers which handle user auth etc. and back-end
mail stores.  The protocol layer servers are fully resilient and you can
fail over a user session at will, but the mailstores don't quite get there:
mail is replicated across different stores, but actions modifying the mail
store are not transactional across all the mail stores. Or in other words,
you can lose a small amount of data if one of the mail stores goes bang at
precisely the wrong moment.  Even so, it will do better at keeping multiple
copies of a mailstore in synch than any locally scripted rsync setup.



Dr Matthew J Seaman MA, D.Phil.                       Flat 3
                                                      7 Priory Courtyard
PGP:         Ramsgate
                                                      Kent, CT11 9PW, UK

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