Mail Update problem

[CahitE]

I think plesk must give up this job !!
This is a brand new linux server which has no error while installing plesk and linux cent os 5.5

after i restore my backups from 10.x to 10.x mail users got the following error :
wrong email pasword or username

and then when i want to update mail box information i got this errors :
if i select Create an e-mail address under your account

then error :

The e-mail address [email protected] already belongs to another user.

Use an external e-mail address

The e-mail address [email protected] already belongs to another user.

both the same
how should i update mail info ???