I'm doing some development which will involve reacting to emails, and I'd like to use a local IMAP mail server for this.
I currently use Devnull SMTP server for testing of sending emails, but this just logs and discards messages, it doesn't do IMAP for checking incoming emails/mailboxes.
I don't need/want a full-blown server, just something lightweight I can easily start/stop as required.
Multi-platform is preferred, but feel free to provide answer for specific platforms also.
(A POP3-based server would also be acceptable for development use, since I'll be supporting both in my code anyway.)
Take a look at hMailServer.