As per article: http://support.microsoft.com/kb/931747 Where is says: The mailbox was created in the Active Directory Users and Computers snap-in on a server that was running Microsoft Exchange Server 2003. does it mean that there is a way to update the Active Directory Users and Computers snap in? Or does it mean that if we want a user with a mailbox we must create them in Exchange Management COnsole, and if we don't want them to have a mailbox we must create them in ADUC? Regards, Alex Davison

Hi Alex, All users need to be created withEMC/EMS including Mailbox-enabled orjust Mail-enabled, Microsoft suggests that don't use ADU&C to create any Exchange 2007 reciepeints. References: Managing User Mailboxes How to Create a New Mail-Enabled User