Exchange 2003/Outlook 2010 никакие правила, но сообщения все еще auto-ccing

You can create this cc rules at different locations. Like you mentioned a user can create himself rules using outlook. Also its possible to create such a behaviour via configuration on the server side.

1. Check for local rules.
2. Check for server side rules / redirects (You will have to check the user A configuration in the active directory)
3. If there are no rules on the server side try to create a new local outlook profile. (System settings --> E-mail, you dont have to delete the old profile just keep it in case there is no change in behaviour)
4. If 1-3 fail the fastest way would be to remove user A (including the mail box) and then recreate the user.