Migrating from qmail: which MTA?

[David Garamond <lists@zara.6.isreserved.com>]

We are planning to migrate a bunch of hosting servers from RH73 + qmail 
+ vmailmgr to Sarge and I'd appreciate on the comments of the choice of 
MTA to use.

Requirements:
- Maildir support;
- Software binary packages are in the main Debian archive (so we are 
guaranteed prompt security updates when Sarge becomes stable);
- IMAPD, POP3;

Optional:
- .qmail support would be nice but not important;
- TLS/SSL support for IMAPD/POP3 would be nice but not 100% necessary;

Other notes:
- I am currently tending towards Courier, but is it widely used by 
Debian users;
- we write our own SMTPD (proxy, actually) because qmail-smtpd sucks, 
and we'll probably retain our code;
- we use vmailmgr for virtual domain users; I don't know how 
qmail-specific it is, and will probably rewrite/reimplement it with the 
new MTA if we must. We plan to retain vmailmgr's virtual users databases 
(passwd.cdb) for the time being.

Regards,
dave