#550 5.1.1 RESOLVER.ADR.ExRecipNotFound; not found ##

Hi All,

 We are using user@olddomain.com and i just convert this user to mail enable user called user@newdomain.com

  I can send to this olddomain from external but internally  getting the above error when sending .

The e-mail account does not exist at the organization this message was sent to.  Check the e-mail address, or contact the recipient directly to find out the correct address.

            < #5.1.1 smtp;550 5.1.1 RESOLVER.ADR.ExRecipNotFound; not found>

 Asa