Mozilla Thunderbird Maintenance

I’ve been using Mozilla Thunderbird as my exclusive desktop mail client at home and work for the last six or eight months. It’s been a perfectly capable and full-feature mail client, it’s not part of the Microsoft monopoly, and I like supporting Mozilla.

Several weeks ago though, my home instance started having problem. The indicator was that the Inbox count (the number of messages) was incorrect, and would often rapidly increase to a huge and incorrect number (200,000+ sometimes). Additionally, checking mail found sometimes fail, and the status bar would display incorrect or irrelevant information.

I did a little research and learned that I should be (have been) compacting my folders regularily to prevent mailbox corruption. To do so, highlight a folder or account, and go File > Compact Folders. Check out How to compact folders in Mozilla Thunderbird for all the details.

I tried several times to compact the folders, but either the process would fail or, if compeleted, wouldn’t fix the program. I concluded after research that this indicated the my mailbox data files had become corrupt. The mail data was OK, but the index, or table of contents of that data was corrupt.

Lukily, Thunderbird can easily create a new index file (foo.msf, for Mail Summary File), and will do so automatically if it finds the file missing. After locating my Profile Folder, I deleted all the .msf files that were causing problems. (Actually ALL of ‘em, just to be safe.) There’s a .msf for each of your mail folders, so your number of .msf files will vary — I had a few dozen.

(To be safe, cut-and-paste a copy of your Profile Folder to a safe location before mucking around in your profile.)

With the bad files out of the system, I booted Thunderbird back up and watched as it rebuilt each index file. Problem solved. It’s been working perfectly since.