Under SME 6.0.1-01, I could program a user's email address as just 'username' in our multi-function devices, and the messages would go through fine.
Under SME 7.1.3, those messages just disappear. I've had to start reprogramming addresses as 'username@domain.com' in order to get messages delivered.
I'm not using DNS, just IP addresses, and everything is in one subnet.
So far this is the only problem with the move from 6 to 7.
edit: I say problem because it's the only thing users are complaining about. Technically, they should have added their full emails when the put the info into the multi-function, but now it's my fault...