> Coda clients are "server" that menage Imap and pop3 connection and write
> email over the coda server :)

Ok, one Coda client, multiple servers. I assume you choose Coda for the
storage failure redundancy and will replicate all data across Coda
servers.

You should build a test system and test its behaviour under high loads. I
do not think anybody has run a similar "high end" setup before.

Coda has some limitations on a directory size, maildirs with lots of
messages can hit the limit.

Which OS are you going to use?

Regards,
--
Ivan