Update:
Threads/posts created on the forum itself are getting sent out, to at least one of the "subscribed" accounts.

It's not going to the other, however.
The one account that is receiving notifications is actually getting two emails, formatted slightly different from each other. One from the proper address. and another from "unknown sender."
(...and I'm not sure what the
-t-95 in the message title is all about.)
I have chosen the "old layout" for emails by the way, it looks less confusing for my userbase.
Also, most importanltly, new threads/replies sent via email... aren't showing up on the forum.
Any assistance appreciated.