- User login in User Profile service: contoso\user1
- Actual user login used by user1: contoso.com\user1
It's obvious there's something wrong. At this situation SharePoint is not able to match SharePoint user with his/her user profile because the user login is "primary key" used to locate the user profile. It means you can't use My Profile page, you can't use information in the user profile like the manager field and job title in workflows etc.
So the question is what is the problem? What we can do to prevent this from happening?
The problem lies in NetBIOS name. Usually the domain name looks like contoso.com and NetBIOS is then contoso. In this case both NetBIOS name and fully qualified name were the same: contoso.com. For some unknown reason (bug?) when SharePoint imports users from AD it trims everything after the first dot. I was consulting it with Microsoft support specialist and his advise was... to rename domain and NetBIOS name. Yes, RENAME domain and NetBIOS name. Wow!
So what is the lesson learned? Never use dots in NetBIOS name... and always check NetBIOS name before installing SharePoint. You can do it easily with nbtstat -n command.