Upon making changes to account properties for Exchange accounts, it may take Outlook up to 48 hours to detect and download the change. If you need to force Outlook to download immediately, the most reliable method can be to delete the Offline Address Books.

Just follow these steps:

1. Close Outlook.
2. Find "Computer" or "My Computer".
3. Open the "C" drive.
4. Navigate to:
   C:\User\<Username>\AppData\Local\Microsoft\Outlook\Offline Address Books\
   Note that <Username> will be your own windows login name.
5. There should be a sub-folder that contains approximately 6 OAB files.
   Delete them. They will be recreated.
6. Reopen Outlook.

ATA