Hello

you can compress the folder and not delete the emails. the whole point of compressing is to make the files lighter. This can be done anytime

Compacting folders has nothing to do with making the files "lighter" and compacting a folder permanently deletes any files marked for deletion. Deleting a message marks it for deletion and hides it from view. Compacting removes the message and frees up the disk space. This article describes compacting. http://kb.mozillazine.org/Thunderbird_:_Tips_:_Compacting_Folders You should also read this about maintaining your file system.http://kb.mozillazine.org/Keep_it_working_%28Thunderbird%29