Comment Qmail + MySQL (Score 1) 484
Well, here in mexico we had the same trouble for us, a large mail system for like 20k users, we switch from sendmail which was ok, but not that fast, to a patched version of qmail to support MySQL databases, also the qpop (latest version) supports MySQL.
You loose the ability to offer shell acces cause the entire password system is on MySQL, but you gain a reliable mail system, which can grow to x numbers of accounts., also you can have the same login more than once on different domains with this system.
You loose the ability to offer shell acces cause the entire password system is on MySQL, but you gain a reliable mail system, which can grow to x numbers of accounts., also you can have the same login more than once on different domains with this system.