One of my clients ask me to set-up a multi server, scalable email system.

I can configure multiple servers to send emails. By using PHP Mysql based login script, users will be redirected to each email server with a login cookie. Domain SPF has all those servers so it can send emails without any issue. (All servers are using a single domain name)

But the problem is when it receives emails MX records can only forward emails to a single server. Is there anyway to forward emails to selected servers.

Or is there any other way to achieve this?

I'm going to use Ubuntu/Debian Postfix, Dovecot, roundcube.

Thanks for any answers in advance.

Note - I think `postfix`'s Transport map is the way to go. But I'm not sure how to configure database and local-part based relay routing.