If you delete a new message without reading it the mailbox icon shows that this account still has new mail in it when it has no new mail anymore and the inbox icon says that you have no new mail. Also, if you get more than one new message, when you open the first one to be read it marks the accoutn as having no new mail even though the inbox folder still shows that you have more new mail.
*** Bug 177124 has been marked as a duplicate of this bug. ***
--- Kevin: does the problem go away if you run Mozilla under a new profile? If the Profile Manager doesn't come up automatically when you start up Mozilla, you can force it to by launching Mozilla from a console window: [(path to Mozilla)]./mozilla -profilemanager Once the Profile Manager comes up, click on "Create Profile". Sometimes bugs like this are profile-related, and the new profile may make a difference - --- The above suggestion to fix bug #177707 had the side effect of clearing the false new mail indicator on the Inbox that I had reported in dupe to this bug, see #177124.
Kevin writes: "For the record I'm not seeing this problem anymore." in TB 220.127.116.11 closing WFM since the TB backend is shared with SM. (this item from comment 0 WFM with TB trunk - "If you delete a new message without reading it the mailbox icon shows that this account")