Disabling old domain users from Person Picker

Question

I have SharePoint 2013 eviorment, There are 2 types of domain users in SharePoint, lets say, that they are old.contoso.com that are old domain users and contoso.com that are new domain users.

Situation:

Now I have a problem, that in default Person picker selects old.contoso.com domain users, but people are logged in to SharePoint with contoso.com users and when there should be approval tasks or other permission dependent occurrence, then that person can't work with those items (since he/she is logged in with different account).

What I have thought of:

1. Removing all old.contoso.com users from SharePoint, but doesn't it affect old documents, if that user can't be find anymore?
2. Move-SPUser - could it work with my current situation?

How could I resolve this situation?

Answer 1

The users from the old domain are still part of the site collection in something called User Information List. This list populates the people picker. You would have to delete the old users from the User Information List which can be found in http://SiteCollectionURL/_catalogs/users.

When you have deleted the users from the User Information List, and the user access the site collection again, the new user information will appear in the user information list. If there are no records in the user information list, the people picker will find information from the User Profile Service (if available) or the Active Directory.