I'm planning to migrate away from Courier to Dovecot - not set in stone, but I'm 99% there.
Why? The following reasons:
- Sieve support
- Really flexible authentication support - I'll probably use SQLite because Cyrus Sasl also supports it, so Postfix can directly authenticate through it
- Actually, Dovecot can act as a sasl authentication server itself, so Postfix doesn't even need Cyrus Sasl - wow!
- Occasionally customers' Outlook versions will have issues with Courier, though Outlook IMAP support has been laughably bad in my experience
- I figured out how to get CRAM-MD5 AUTH working with Dovecot!
This will take awhile, as I'm planning to revisit my entire email services setup.