We are using Microsoft Outlook 2002 SP3.
I appreciate that you subsequently need to connect to the server for the emails to be deleted. Outlook is set to send and receive on a 5 min timescale, as we have Broadband and are continually connected.
Even when we do a manual send and receive, we still have the problem.
I have two other computers that collect my email too, and they are set up in the same way. They delete the emails (mainly Spam) from the server when deleting from the "deleted Items". However, these do not have avast on them, only Norton Internet Security.
The only thing I can see as different, is avast.
When you delete from the deleted items, the avast icon flashes in the tray at the bottom Right Hand side of the window. This leads me to believe that it is having some action on the deleting process, and therefore, incurring the problem as mentioned.