How to change squirrelmail login username "john" to "[email protected]" ?

I have setup postfix,squirrelmail and fetchmail.

When i want to enter squirrelmail or Outlook express then i only need to enter john and not [email protected]

How can i set that when i want to acces squirrelmail then that i have to type [email protected] instead of just john.

My outlook express username also were [email protected] but now its only username, when i try [email protected] then it wont take it.

I wonder if the emails is been delivered to the people on my server??

Any help would be appreciated

 

Do you use system users or virtual users in your setup?