Error ID 72e9 Error in resolving user ‘ABC’: System.DirectoryServices.DirectoryServicesCOMException (0x8007202B): A referral was returned from the server...

When you have used PeoplePicker conrol in SharePoint 2010,  you might get below error instead of the user from Active Directory Services:

Error ID 72e9 Error in resolving user ‘Alpesh’ : System.DirectoryServices.DirectoryServicesCOMException (0x8007202B): A referral was returned from the server...

I found a solution provided at Joel Jeffery's blog with following details
We had a weird problem at one of my customers the other day. They’d built a SharePoint 2010 farm with one web application and three site collections.

In two of the site collections, the PeoplePicker control allowed the users to select the correct folks from their Active Directory. However, for one site collection, only users that already exist in the User Information List

could be resolved by the PeoplePicker....

Click here to read the original article

/Alpesh