The original question has been answered already, but JFTR:
Carlos Williams schrieb:
> I don't
> think this is an issue on Thunderbird or any other client since
> Outlook is the only client I have seen that requires you to purge
> deleted messages rather than simply deleting them and then emptying
> the trash.
Thunderbird and Seamonkey have a configurable deletion model,
using either a Trash folder or the IMAP Deleted flag. But the
support for the IMAP Deleted flag is rather lacking, and for
that reason most users prefer the Trash folder model, even
though technically it runs against the concept of IMAP.
Under the hood, the Trash folder model works by copying the
message to the trash folder, then marking it as deleted in
the original folder, and finally purging the original folder,
just like Squirrelmail, so you end up having the same sort of
effect you described.
Phoenix Software GmbH