We have a complete copy of our infrastructure in our test lab, three DCs, single Exchange 5.5 server, and we have been completing a migration from Exchange 5.5 (single server, single organization) to Exchange 2003, everything appears okay, BUT users mailboxes that have been migrated from Exchange 5.5 to Exchange 2003 servers no longer have access to the Global Address List when using Outlook 2000 or Outlook XP client. Outlook Web Access and Outlook Mobile Access clients work correctly. We have checked MAPI, RPC communication, enabled diagnostic logging, checked the Global Catalog servers, checked the DCs, checked replication, but still cannot find a reason for why this is occurring? Could anyone else think of anything else we should check? Regards Andrew -- No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.1.371 / Virus Database: 267.14.8/215 - Release Date: 27/12/2005 -- No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.1.371 / Virus Database: 267.14.10/218 - Release Date: 02/01/2006