Last night, I checked some changes in for http://bugzilla.mozilla.org/show_bug.cgi?id=114379 that make it so we store message labels on the imap server if the imap server supports user keywords. If you use message labels on imap messages, and you are using a server that supports user keywords, you should be aware that at some point in the near future, your local label settings will be lost unless you relabel your messages so that the label values are stored on the server.
I'm not sure if this will affect anyone, but this is just a heads up. You can read the comments in the bug for more details. - David
