[plug] good mail server?

[Craig Ringer]

Hi folks

I'm looking into implementing a mail server on our linux gateway machine 
to replace an ageing and rather poor NT based mail server. I was 
wondering what experiences folks here have had with various mail 
servers. The SMTP server side is less important than client-side access 
via POP3 and IMAP. A nice IMAP server is a key priority, preferably one 
that can decode messages to allow clients to download message bodies but 
not attachments (until requested).

I've had a play with cyrus, and it seems to be powerful but fragile and 
quirky. Migrating messages is a priority. The current mail server uses 
the RFC822 message format, while I think Cyrus uses its own custom mail 
store.

So - any experiences with Courier, Cyrus etc that folks would be willing 
to share?

Craig Ringer