How often have you run around and made sure everyone was out of Exchange ,when you need to perform maintenance or upgrades on your Exchange Server, only to have some bozo log back in midway before you have finished.

There is a way around this. Follow these instructions.

1). Stop the Information Store Service on the Exchange server.

Use Regedt32

2). Locate the HKLM\SYSTEM\CurrentControlSet\Services\MSExchangeIS\ParametersSystem registry key.

3). Add a "REG_MULTI_SZ" Value with the value "Logon Only As"

4). Type one line for each allowed user. Use the following format

/o=organisation/ou=site/cn=container/cn=UserID

For example - Assuming your Exchange Organisation Name was OutlookExchange, the Exchange Site was NORTH AMERICA and you wanted to allow a user called Colin Janssen, who's mailbox resides in the RECIPIENTS container, you would enter the following

/o=OutlookExchange/ou=NORTH AMERICA/cn=RECIPIENTS/cn=Colin Janssen

5). Close Regedt32 and Restart the Information Store Service.

When a user who is not listed tries to connect to the Information Store , the user is greeted with: "The set of folders could not 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.

When you are done performing your maintenance:

1. Stop the Information Store Service.

2. Delete the Logon Only As value name.

3. Restart the Information Store Service.

Export this registry entry and keep it handy for the next time you need to do this.