Nickname and e-mail addresses

Hi all,

I have a problem with e-mail addresses and nicknames in my second post-office.
In the first poa you can view a users nickname e-mail addresses (and mail to it) but on the second poa you cant see users nickname e-mail address and you get a bounce if you e-mail it from the outside.
I can see that it is any really difference between the settings of the poas, exept in the second poa users are only know for a specific domain name.
Anybody got a idea?