> There will be 2 mail servers, mail1 and mail2
>
> Any email that is received by mail1 should automatically be forwarded
> to mail2, and any email that is received by mail2 should be forwarded
> to mail1. The only exception to the rule is when they receive messages
> from each other.
>
> Thus a user can check their email via IMAP or (shudder) POP from
Why shudder? POP is by far the most reliable service of the two and
much simpler and supported by more clients.
> either mail1 or mail2. If either server goes down, the other one
> should be receiving messages. The moment the server comes back up, it
> should receive all the messages that the other received during the
> down time.
>
> Is this a good way of providing redundancy? Or am I better off with a
> different mechanism?
This is not a very good mechanism particularly. First off, when they
delete an email on mail1, how will the copy on mail2 get deleted?
Second off, it seems that the user will have to know whether mail1 or
mail2 is the server that is available. That's not very user friendly.
> Can qmail be configured this way?
It can, but I doubt anyone will recommend such a setup.
The typical solution is to put the mailboxes of the users onto a
single, very reliable, piece of hardware (made reliable by redundancy
or high quality componentry or both), then use as many front-end
servers as needed to handle your redundancy requirements, load and
budget.
Remember, if the mailboxes are in Maildir format, they can safely be
shared across NFS. A simple configuration might be:
1. A single high-availability NFS server - pick something that
supports RAID and has parts that can be replaced quickly and
easily.
This doesn't have to be something expensive like a Netapp -
though they are good for this. It could be something cheap
like an Intel BSD as long as you have spares on the
shelf. Don't use Linux for NFS serving - my experience is that
it's too buggy. Any of the other free Unixen will do the job -
pick the one you know best.
Spend as much money on this box as you can.
2. A number of front end SMTP and POP servers. These front-end servers
mount the mailboxes from the NFS server. These front-end
servers don't need a lot of disk - just enough for the
mailq. Any of the free Unixen will do for this - pick the one
you know best.
3. Use the DNS (or a load balancer if you have more money, but I note
the .edu address) to present these multiple front-end servers
as a single name/address to your user community. I recommend
something like smtp.yourdomain and pop.yourdomain.
> Since I have never set up qmail before, detailed explanations would be
> appreciated.
It's not really specific to qmail, but Maildir makes this a much more
viable solution compared to the locking and performance nightmares
associated with V7 mbox format used by sendmail and mail.local.
Regards.
