Set AD SPN record for MS SQL service account

 Source

1. Granting read/write servicePrincipalName permissions to the service account using ADSI Edit, as described in https://support.microsoft.com/en-us/kb/811889
2. Removing the SPNs that previously existed on the SQL Server computer account (as opposed to the service account) using
   
   

   setspn -D MSSQLSvc/HOSTNAME.domain.name.com:1234 HOSTNAME

   
   where 1234 was the port number used by the instance (mine was not a default instance).