Hey GameCon,
Here's what I got from dthadmin in my ticket which solved the mail problem for me:
You have a setup issue. Go to Configuration -> Emails. Then check the Admin notification email. It's blank! You need to configure this email AND subject. The warning you get is because it's trying to send that email and there's nothing there.
Also, you need to fix your thanks email as you have some old dead tags there like [CONTACT_DETAILS]. Only use tags that are seen on the left of the emails.
It wasn't (and in my still isn't) intuitive that we are *required* to put anything in that field, but it does make sense. Hopefully this fixes things for you. It didn't fix everything for me as you've read in the thread, but it helped that specific mailing problem.
The rest of the answer, which also might apply to you was answered this morning in my (closed) ticket:
I see on your
http://xxx.xxxxxxxxx.org
site, you do not have BCMath enabled in php, which is needed with changes that were made in 2.7.2e. This was not an issue for most people, but as it has been for some, the 2.7.3 package, due out in another day or so, removes the BCMath need again.
without that, in 2.7.2e, you will not have any success with paid registrations. So either jump back to 2.7.2c until we have the new package ready, or get BCMath enabled in your php configuration.
Sorry for the inconvenience.
So you might be fixed by going back down to 2.7.2c as well. For me, I'll stay where I'm at in "blank confirmation" mode until the new release is put out which (crossing fingers) fixes my issues once and for all. I might even go so far as reload an old backup which will restore my 18 months' worth of history too, but am not sure at this point.
Hope that helps...
Cheers!
-soccerbum