Error [ERR] Email 'xxx.yyy@xxxx.cz' is already taken

What should be the correct administrator action if there is an entry in the log
[ERR] Email 'xxx.yyy@xxxx.cz' is already taken out of sync with AD?

The administrator should make sure that the email is entered correctly and is not duplicated (in Active Directory)

Error occurs if the user is manually modified e.g. changing the username in Infoport.

It is recommended to track the change and edit it in Activ Directory or Infoport. 

Alternatively, the user can be deleted in the Infoport database, after synchronization with AD, the user is re-established in Infoport in the correct way.