To keep user out of Exchange while you perform maintenance or an upgrade:
1. Stop the Information Store Service on the Exchange Server.
2. Use Regedt32 to navigate to:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MSExchangeIS\ParametersSystem
3. On the Edit menu, Add Value name Logon Only As as a type REG_MULTI_SZ value.
4. In the Multi-String Editor, type one line for each allowed user. Example:
/o=microsoft/ou=apps-wga/cn=recipients/cn=YourUserID
/o=microsoft/ou=apps-wga/cn=recipients/cn=YourCo-Worker
5. Exit Regedt32 and Start the Information Store Service.
When a non-listed user tries to connect to the Information Store, they are greeted with:
The set of folders could be opened. The attempt to log on to the Microsoft Exchange Server has failed
NOTE: If you leave the Logon Only As string blank, no one can connect.
NOTE: When you are done performing your maintenance:
Stop the Information Store Service.
Delete the Logon Only As value name.
Start the Information Store Service.
