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The folder C:\Documents and Settings\MyName\Application Data\Thunderbird\Profiles is using 8.35 GB disk space which is huge. Since I need to back it up, I deleted maybe 50% of mail, including everything with attachments, and that folder still takes exactly the same amount of space, that is 8.35 GB. What can be wrong? I tried to close the application, to reboot the PC, nothing helps. And it was Shift+Delete, i.e. Trash folders are empty.

Thunderbird version 3.1.2
Windows XP Pro

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up vote 5 down vote accepted

Thunderbird uses large files to store multiple messages. When deleting, it only marks the message as deleted. You need to compact the folders to reclaim the space used by deleted messages:

The easiest way to compact is to let Thunderbird do it automatically: "Tools -> Options -> Advanced -> Network & Disk Space -> Disk Space -> Compact folder when it will save over 100 kB -> OK."


To compact all folders in an account manually, click the account on the left, and then click "File -> Compact Folders". This has to be repeated for each account. Compacting an account may take from a few seconds to 10 minutes or more, depending on how much mail you have and how recently you last compacted the folders. If you have trouble doing this and the process stalls, try compacting one folder at a time by right-clicking on the folder and choosing "Compact" ("Compact This Folder" in older versions). If you do not let Thunderbird compact automatically, you should do this regularly, at least once a week. If you do it daily, it will take only a fraction of the time.

But, as meanwhile your message file has become huge: be careful. If possible, first try to backup your profile folder, and before you start: read the other instructions.

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Open the trashcan within Thunderbird. Do you see any mails in there? If so, delete them once more. Does that reduce the disk usage?

If so: Open "Properties..." in the context menu of "Local folders". There should be an option "Empty trash on exit". Check that and the mail should be gone.

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Recycle bin is empty. Checking "Empty thrash on exit" had no effect.. – Sejanus Sep 5 '10 at 11:44
Did you check the recycle bin on the desktop of the one inside Thunderbird? – Aaron Digulla Sep 5 '10 at 12:56

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