This is not really a bug, but a usability issue. We have an IMAP mail store which users access with Thunderbird or other clients when onsite, and with Squirrelmail when borrowing someone elses computer, using a kiosk etc. If they normally use a Trash folder in Thunderbird, they can select the same one in Squirrelmail and get the same functionality. But if they use mark-as-deleted in Thunderbird, and don't have a Trash folder, then in Squirrelmail if auto_expunge is off when they delete a message it is gone immediately, contrary to expectation from using Pine, Thunderbird etc.., while if auto_expunge is on then users with a Trash folder
have to expunge as well as delete and purge trash.
So it would be nice if users with no Trash folder
set auto_expunge false, and users with a Trash folder could set it true.