Address format changed after upgrade

I upgraded a client to 7.0.3 and now the sender has his emails sent, not in the format user@companyname.com but Firstname Lastname/Company@companyname.com.

I looked in his location doc for clues, but nothing jumps out at me.

No one else is affected so I am presuming that it is local to his intallation.

He also uses a PDA, so I am not sure if that would have replicated his old contacts back to his new install and somehow changed something? That is the only thing I can think of that makes his install differ from anyone elses.

Any clues anyone please?