On a SBS 2003, I changed a user logon and email as explained in the following http://www.experts-exchange.com/Software/Server_Software/Email_Servers/Exchange/Q_22744744.html
I had to rebuild GAL and recreate the outlook profile to have the correct name of the user in Outlook.
Problem : when the user try to send an email, the from address is still the old email address, the user can change manually the from address with its new address and send the mail normally.
I made the change 4 day before, so I don't think Exchange is that slow to make the change.
Any idea ?
PS: I don't have remote access to the server, and will be tomorrow on site, so without solution I will create a new user with correct information and delete the old one