Now and then (sometimes once a week - sometimes multiple times per day) Thunderbird looses the ability to move messages to folders. Typical symptoms are: Send a message - message sends fine - then it hangs forever with the dialog box saying that it is copying the message to the sent folder. (I have allowed this to sit for hours - it never completes.) If I cancel copying it to Sent, it wants to copy to Drafts - but it hangs doing that too. Filters that move messages don't work. The mail archiving feature doesn't work. (no error message no hang - simply does nothing.) Junk controls mark messages as junk but don't move the messages to the junk folder. All of the above can be remedied by simply shutting down Thunderbird and restarting it. Then it will be fine for anywhere from 5 hours to 20 days before this occurs again. I am using a pop account with local folders. All of these moves are local to my PC. I have only been using Thunderbird for a few months so all of my folders have small numbers of messages. My drafts folder typically has zero messages (and the file is zero bytes) and it still can't copy to it. I am running Windows 7 64 bit - installed about 3 months ago, Thunderbird 24.6.0. (The problem occurred with the previous version of Thunderbird as well.) Lots of available disk space. Some non-default settings: Thunderbird is set to use a global inbox (local folders) and the local folders have been relocated from the default location to my user directory on drive D: TB is set to not check for email automatically or on startup. There are two accounts. I'm using the enigmail, quicktext and allow-html-temp extensions. Though I have typically not used any of these around the time that it starts hanging. Since it can take weeks to appear, it's difficult to run safe mode or extension-less for such long periods.