Thunderbird - Question

I have a file "Inbox" (no extension), that contains 41,707kb = 40,7mb, while all my Local Folders (Inbox,Unsent,Drafts,Sent,Trash) are EMPTY, because I cleaned them myself.
40,7 MegaByte doesn't sound empty to me and this file seems to grow every day.

The complete path of this file is :
C:\Documents and Settings\Erik\Application\Data\Thunderbird\Profiles\7hrs4k32.default\Mail\Local Folders\Inbox
Keep in mind that the folder "Application Data" is hidden.

Is there a way to clean this file "Inbox" via some setting or function in Thunderbird ?

Thank you in advance.

EDIT :
Found a solution. Case closed. Pffft.

 

Erik: Don't know if you saw it but there is a setting in T-Bird that can ask you to compact the folders after they reach a certain size. I set mine to 250 KB (see attached)

You can also use a T-Bird extension called Xpunge to give you handier, manual control of the situation. https://addons.mozilla.org/en-US/thunderbird/addon/1279

 

there was a thread at ubuntu forums a few months ago about how TB keeps all your email even if you think you have deleted it. in the thread someone showed how to really get rid of deleted email. is that the same thing?

http://ubuntuforums.org/showthread.php?t=238444

 

Yes, it is indeed the same thing.

One thing I don't quite understand is that if T-Bird will handle the compacting on it's own, why not make that the default setting? Or make it clearer during initial setup that it's something to check periodically?

But they don't...

 

Thanks but that was my solution in my original post. See my EDIT in post #1.