I'm using Ubuntu 12.04 and I just found out my .thunderbird folder under my user home directory is 7.4 Gigabytes... However I'm pretty sure I'm using IMAP for all my email accounts, so why is it so huge? And what should I do? Can I just delete the .thunderbird folder?

3 Answers 3


For IMAP accounts, offline folders are enabled by default, so a copy of all mail is kept locally.

To disable it:

  1. go to Account Settings -> Synchronization & Storage and uncheck "Keep messages for this account on the computer".
  2. under Account Settings -> Server Settings, take note of the relevant "Local directory".
  3. exit Thunderbird
  4. in that "Local directory" and it's subfolders, delete the mailbox files (the files which have no extension). But keep the .msf index files and the .sdb files.

You may also want to disable "Global Search and Indexer" under Preferences -> Advanced -> General.

See http://kb.mozillazine.org/Minimize_the_size_of_a_profile for more details.


It is probably cache and emails you read, thunderbird needs to download them for you to read, even if you use IMAP. You can start by cleaning the cache: http://www.techiecorner.com/1737/how-to-clear-thunderbird-imap-cache/

Or you can use compacting: http://kb.mozillazine.org/Compacting_folders

  • 1
    That link shows where to delete the cached mails, but the files will be recreated. The offline cache needs to be disabled in the preferences first.
    – mivk
    May 20, 2014 at 8:58

It seems that you are storing all your emails and attachments (7.4 GB of them). By default, thunderbird downloads all emails and mirrors them locally. If you delete some of the bigger emails in the cache, this will decrease the size of your thunderbird directory.

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