Transparent redirect to another interface ?

[Frank Bonnet]

Hello

I have a new mailhub with two ethernet gigabit interfaces, and I would like to
transparently redirect IMAP or POP3 requests to the second interface which
have a different IP address, to let the first interface drive the SMTP traffic only.

Is it possible ? This will avoid thousands of email clients re-configuration to
let users grab their incomming emails.

Any info welcome.

TIA
Frank