Re: [exim] Multiple Mail Servers

matt@??? wrote:
> Hello Everyone,
>
> Merry Christmas to everyone and i hope you all have a happy new year.
>

Merry Christmas and 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,

It will mostly depend on your database application but it works with
most recent databases.

>and also replicate the files in /var/spool/mail using unison
> once every 30 minutes (it will only replicate if files have changed).
>

Unison works very well for that, but you have to configure it very well.
You should consider using recent devel versions of unison as they have
some means to do clean reconciliations.
You should also use dovecot with a recent version as there are some
improvements for replicated filesystems with indexes.


> 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?

In fact, I do all that for receiving and sending (basic load balancing
with 2 IP for 1 A record), with smtp (exim obviously), pop and imap
(dovecot) without any problems. You should only ensure that the mail
volume could be replicated fast enough with unison.