MODSEQ

I'm having the exact same problem. And it seems to have started on the exact same day (Dec. 8th). The choices on the popup menu to "Retry", or to "Try Later" never solve the issue, and the third choice, "Take Account Offline" isn't practical. The message can't be ignored because it keeps popping up. While the message is up, MailMate shows the spinning beachball rendering the application "frozen".

Sorry about the late response! I think this might be fixed. (It's related to IMAP historically only handling 32 bit values, but it's now allowed to use 64 bit values -- something MailMate did not handle everywhere.)

Hold down ⌥ when clicking “Check Now” in the Software Update preferences pane to get the latest test release (r6015).

Hi Benny,
Thanks for replying. Actually, after about three days, the issue mysteriously disappeared. I had been using release 5937 at the time, and still am.

And as a side note, when I click "Check for Update", it tells me that 5937 is the latest version available. OK, but when I hold down Option, as you suggested, "Check for Update" turns into "Check for Test Build", but when I choose that, I get the same result as if I didn't press Option. That is, I get a notice that the version I have installed, 5937, is the latest version available. I.e., no effect from pressing Option other than the menu item name changes. Simply said, I'm not able to upgrade to 6015. (Not that I see any need to anymore, since the issue has resolved itself.)