I'm planning out a project (web/mobile app) that would require a mail server that could handle hundreds of thousands connections per hour (both IMAP/POP and SMTP) and has the ability to interface with PHP (or python or whatever) to dynamically create, delete and check for mailboxes? This is not for spam stuff, I just need my app to generate random mailboxes (and static/permanent ones too) to receive mail and process it for items listed on my service. The little research I've done so far has turned up courier, dovecot, cyrus and haraka. I think the ability to scale and/or load balance (I'm new to these terms, pardon me) would also be a requirement.

Any ideas?