SMS Email Gateway bad address syntax?

I'm trying to use the E-mail Gateway module included in the SMS Framework. When I confirm my phone number, it works. But when I set my user's Messaging and Notifications default send method to SMS, the notifications don't work.

It looks like it's trying to send messages to <5555555555@>. The returned mail says "bad syntax". I think it's supposed to be sending to 5555555555@txt.att.net.

Any suggestions would be greatly appreciated.