After making changes to users or groups, users may report that the information reflected in the Global Address List is incorrect. The issue usually is that the GAL has not been updated yet, so to correct the issue, you must force an update.
To update the Global Address List:
1. Open the Exchange Management Shell
2. Issue the command: Update-GlobalAddressList -Identity “GALNAME” and press Enter.
(Be sure to replace GALNAME with the name of the list you wish to update.)
If you do not know the name of the address list you are trying to update, issue the following command:
The console will return any Global Address Lists that belong to the Exchange Installation.
Issuing the command to update the Global Address List will start the update process, however it may take much longer for the list to actually be updated