[kevinh]

First problem (repeat messages) is almost certainly due to messages being left in the forum mail box. If you are using IMAP in "Email Reply Integration Settings" (in Forum settings) - try switching to POP.

Beforehand however, you might want to go into the mailbox using a web client and delete the exisitng messages so you don't further irritate your subscribers

Can't suggest anything for the second problem, other than checking that the message is actually making it into the forum inbox and obviously making sure the sender address is that of a registered user with appropriate permissions.