To delete messages from the VPOP3 'OutQueue':
Note that you cannot delete items from the VPOP3 OutQueue whilst VPOP3 is in the process of sending them, so you should stop VPOP3 from sending first.
If there are too many messages in the outqueue and you cannot delete them using the above method, you can delete all the messages them the 'backdoor way'. To do this, stop VPOP3, then delete all the Q*.DAT files in the VPOP3\Outqueue directory, then restart VPOP3. (Note that doing it this way, you can't be selective about which messages you delete).
If you want to save some messages, you could move the Q*.DAT files into another folder on the disk, then move them back in smaller chunks, deleting the unwanted messages as you go.
If the messages are in the outqueue due to a problem of some sort, it can be worth keeping some of the Q*.DAT files for diagnostic/forensic purposes.
If there are too many messages in the outqueue and you cannot delete them using the above method, you can delete messages by accessing the database directly.
If you know the IP address of the original sender of the messages, type:
DELETE FROM outmessages WHERE senderip='<sender IP address>';
and press Do Query
If you know the authenticated sender of the messages, type:
DELETE FROM outmessages WHERE authsender='<sender user name>';
and press Do Query
Otherwise you will need to empty the outqueue totally, so type:
DELETE FROM outmessages;
and press Do Query
If you cannot start VPOP3, or get into the VPOP3 settings, then you can delete outqueue messages directly from the database.