[exim] Multiple Mail Servers

Hello Everyone,

Merry Christmas to everyone and i hope you all have a happy new year.

I am currently trying to setup multiple mail servers so should the smtp
server go down, we will receive mail to our of our other smtp servers,
then when the original server comes back, the mail is passed on there.

I have the following setup.

Mail is stored in /var/spool/mail/domain/username (maildir format)
Users/Domains and a few other stuff is stored in a database.
For pop3/imap im using dovecot.

Could i replicate the sql database to another server, eg, my secondary
mail server, and also replicate the files in /var/spool/mail using unison
once every 30 minutes (it will only replicate if files have changed).

Then use a more or less identical config file on the secondary server...
because all users and mail data will exist on that server, although this
server will strictly be for receiving mail... i dont plan on sending any
mail with this server.

So although the exim server itself is acting more or less as an
independant server on both hosts... the use of sql replication and unison
will keep them both in sync, and since im using maildir inbox format, i
cant see any problems with replicating /var/spool/mail because i dont have
to really worry about file locking because each mail goes into a new
file... also appended

Can anyone see any potential problems with this method..... or do you
think it will work fine?

Thank you.

Matthew Jones