We've migrated from Exchange2000 (OldEX) to Exchange2003 (NewEX). OldEX sits in an org belonging to our Win2K AD (OldAD) - NewEX sits in an org belonging to our new Win2K3 AD (NewAD). (There's a trust in place between OldAD and NewAD) All the permissions to the mailboxes have migrated across as required. This means that UserA can log on to his migrated account in NewEX using both his OldAD and his NewAD account. When UserA logs onto his mailbox using his OldAD account, he gets this problem (i.e. he can only see other peoples calendars if they have granted "default" "reviewer" access, even when UserA has been granted i.e. "owner") If UserA logs on to his mailbox using his NewAD account - everything works fine! Thanks in advance!