Cyrus is discussed at a few official mailing lists hosted by Topicbox — which is, itself, powered by Cyrus!
At the links below you can browse the archives and subscribe to the lists. You can request a daily summary if you don't want to receive every message in real time.
This is a low-traffic mailing list used only for announcements related to Cyrus releases.
This is the general mailing list regarding all aspects of Cyrus software. The bulk of the discussion is about the IMAP server.
This is the mailing list specifically about the Cyrus SASL library.
This is a mailing list for the use of Cyrus developers and package maintainers, for all the Cyrus software.