Sam Brown

Compact Folders in Mozilla Thunderbird

“Need to save some space on your HDD? Making a backup and wondering why your Thunderbird Profiles folder is huge? Confused? I was too until I found Compact Folders!”

I have been using Mozilla Thunderbird as my email client for a long time now, since version 0.5 at least, and it really is a brilliant client. However, recently when I went to backup my computer before installing OS X Tiger I noticed that my Thunderbird Profiles folder, where all the emails are stored on my hard drive was 795MB in size.

This didn’t really shock me much at first as I do have a lot of emails and a lot of big emails in my various email accounts and Archive folders. Four POP3 accounts to be exact!

Deleting emails… doesn’t delete emails?

Pressing Delete on an email in your Inbox moves the file to the Trash folder, Emptying the Trash folder removes the email from there and hides it from you! Yes, that is right. When you empty the trash in Thunderbird the emails that were in there are now gone, but are still there hidden from you. Make sense to you?

When you delete or move e-mails from a folder, Thunderbird and other e-mail programs really only “hide” them (i.e., mark them as ready for permanent deletion), and these hidden e-mails still actually remain in the folder. Even emptying the Trash does not permanently delete them. These hidden e-mails remain in the folder until it is compacted.

Does this not seem a little strange? It sure does to me! I went ahead and deleted all the big emails that I never needed anymore from my Archive folders. Mainly pictures, spam emails and attached files that I no longer needed. Quit Thunderbird and checked the folder size.. still 765MB. A quick search in the Thunderbird Forums didn’t prove much help until I saw someone comment on a post about Slow sending emails to try and Compact Folders, what’s this I thought.

How to Compact Folders

To Compact your folders in Mozilla Thunderbird all you need to do is select the account in the Folders pane and go to File Menu > Compact Folders. This may take a moment and will only work on that account, if you have multiple accounts you will need to do it for each.

After selecting all four accounts and Compacting their Folders my Profiles folder had dropped from 795MB to a cool 75MB.

Can’t Thunderbird Compact folders for me?

Infact, why does Thunderbird not just delete those emails that I told it to delete? This I really don’t understand, and a quick search about the Mozilla site didn’t really bring any good reasoning to my attention. This quote I did like however:

If you don’t compact folders, your mail folders can grow very large and erratic program behavior can occur, so it’s a good idea to do it periodically.

At what point were they going to tell me to do this? They weren’t and didn’t! I wasn’t really having problems I just wondered why deleting several hundred megabytes of emails didn’t even make a dent in the profile folder size. I see this as a major flaw in Thunderbird, especially if people do experience erratic problems, and I bet plenty of people have much larger inboxs than I have.

Thunderbird should purge these files monthly for you, or, as one would expect, empty the trash properly!

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Sean 8 June 2005, 03:45 #1

Seems pretty weird that it wouldn’t just do it automatically, or at least purge after a month or so – if in fact it’s supposed to be a ‘feature’ for when you go ‘oops’...however, you’d have to put them in trash and also then accidentally delete them.

Anyway, ‘bgz’ as is! ;)

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Sam Brown co-founded Iterate, and was previously VP of Design at Foursquare. Based in NYC.