Since 5.1.2 was rushed to patch that nasty account bug in 5.1.1, there were a couple bug fixes and features that didn’t make it into that release that were almost done. Finally, you can see the first of the new really awesome features I’ve been working on that required “breaking” core functionality to make them happen: IMAP now uses server-side tracking of read/unread status instead of local tracking, for those who check their email from multiple devices. POP3 will continue to track read/unread status locally.
* IMAP uses read/unread status from the server instead of tracking locally
* IMAP shows message as “important” if it is starred/flagged on the server
* Recent beta changes to quick check algorithm caused unnecessary full check when quick checking.
* Leaving IMAP account connected between checks (introduced in 5.1.2) is buggy when multiple IMAP accounts. Rolled back for now.