Liam, thank you so much for finding a solution! You are a godsend.
I had trouble at first, though. Maybe this will help someone else: Try copying EmailShield.ini to another location first, then edit the file, disable Avast's Self-Defense Module temporarily, cut and paste the edited file to the original location, and then turn the module back on again.
Please, Avast team, place these options under another menu. Have it in the next update! Believe me, customers will be very grateful.