We don't do a good job keeping these pages up to date so you will want to subscribe to the appropriate mailing lists for the release announcements and check the FTP site for newer versions. The documentation is located in the doc directory of the distribution. Please be sure to read the files in that directory after you unpack the distribution. The latest version of the IMAP server is 2.0.16. This is now a production release and we are running this code base internally.
Older versions are also available.
However, no further development is occuring on the older versions of the software. If you'd like to send a patch, we'll review it and possibly make another release but bug reports against older versions are likely to get a response of 'upgrade to the newest version'. From the 1.6.x generation, version 1.6.24 is the current stable version. Version 1.6.27 has a few compilation fixes but is considered BETA for now. From the 1.5.x generation, version 1.5.24-BETA can be downloaded.