Dear Janine:
Thanks very much for the advice! The thing is, I don't know where to reset that notification_user_map.sent_date: do I find these messages in the postgre database, and if so, might you know the table name? (you are free to tell me to go look up the tables myself, I suppose it is time for me to study them in detail).
I've checked the EmailReplyAddressPrefix for extra spaces already and there are none.
Brian: thanks for the M tip, I'll do it.
Thanks!
Bruce