Changing the Microsoft Exchange Organization name can be complicated. If you change the Microsoft Exchange Organization name, you must reinstall
Microsoft Exchange Server on all servers in all sites.
This article explains how to change the name of a Microsoft Exchange
Organization.
NOTE: You must create new client profiles for all users with mailboxes within the site. The Outlook client profile caches the X500 directory name of the mailbox server.
If you do not create a new profile, you may receive the following application event IDs on the server:
Event ID: 1023
MsExchangeIS Private
Type: Failure Audit
Category: Logons
Description: Domain\User was validated as
/o=ORG/ou=SITE/cn=Recipients/cn=USER
but was unable to log on to /o=OLDORG/ou=OLDSITE/cn=Recipients/cn=USER.