If the primary Windows NT account for a mailbox is changed, the new primary Windows NT account does not have immediate access to the mailbox and the previous primary Windows NT account still maintains access for some period of time.  This problem may also occur after a move mailbox operation.

It's because of the information store caches information contained in the directory store and, by default, it re-reads it every 120 minutes. Therefore, any change to a directory object (for example, a primary Windows NT account change) is not reflected in the information store for two hours.

To have changes to directory objects picked up immediately by the information store, follow these steps:

1. Run Registry Editor (Regedt32.exe).
2. Locate the following key: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MSExchangeIS\ParametersSystem
3. On the Edit menu, click Add Value.
4. Enter Mailbox Cache Age Limit for the Value name.
5. Type REG_DWORD for the Data type.
6. Type 1 for the Data of type DECIMAL, and then click OK.
   
   NOTE: This registry entry is not a switch, it is a setting. If it is set to 1 the server rereads the cache every minute; if it is set to 2 the server rereads the cache every 2 minutes, and so forth.
   
   
7. Stop the information store service.
8. Restart the information store service.

The information store now updates its mailbox cache frequently by rereading the directory every minute. 

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