Exchange 2003 Reached 16 GB Mailbox Store Limit

I also saw the message below:

When I examined the application event log on the Exchange server, I saw the following entry listed:

Event Type:	Error
Event Source:	MSExchangeSA
Event Category:	MAPI Session 
Event ID:	9175
Date:		5/1/2006
Time:		12:35:52 PM
User:		N/A
Computer:	S
Description:
The MAPI call 'OpenMsgStore' failed with the following error: 
The attempt to log on to the Microsoft Exchange Server computer has failed.
The MAPI provider failed.
Microsoft Exchange Server Information Store
ID no: 8004011d-0512-00000000 

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I did not see an immediate cause for the problem. Rebooting a client workstation did not resolve the problem, nor did rebooting the server.

Checking on the event log entry, I found the following advice from Microsoft for troubleshooting the problem:

Details 
Product: Exchange 
Event ID: 9175 
Source: MSExchangeSA 
Version: 6.5.0000.0 
Message: The MAPI call 'value' failed with the following error:

error code 
    
Explanation 
This Error can be triggered under a variety of conditions:

When mounting a mailbox store or public folder store. 
When the System Attendant is trying to generate an Offline Address Book. 
When the stores are down and the SA is trying to do its routine management tasks. 
When attempting to perform a Move Mailbox operation. 
At the rate of 1 every minute on a Clustered Exchange Server. 
In essence, this message indicates that the System Attendant process has been unable to log on to the Mailbox Store or Public Store.

There are several flavors of this event. The ID number in the Description section of the event will be the only difference between the events. Depending on what the underlying cause of the problem is, the ID number will vary. The other ID numbers that might be seen are: 8004011d-0519-0000000, 80040111-0286-00000000, 8004011d-0289-00000000

There could be several causes for this event, but the main ones to look for are:

Information Store (IS) is not running. 
IS is running, but one or more databases are not mounted. 
The Read System Access Control List (SACL) of Exchange Enterprise Group is lost. 
Inappropriate permissions on the MDBDATA folder 
System Attendant Service is running with a different user account than "Local System". 
The Default Public Store attribute on an Exchange 2000 server points to an Exchange 5.5 server public store in another domain 
The System Mailbox object that is created for this mailbox store exists in the Microsoft Exchange System Objects container 
 
    
User Action 
While the proper resolution will be determined by the ID number that shows up in the event, you can try the following actions:

Verify that the Information Store is running. 
Make sure that the default mailbox store is mounted. 
Run setup /domainprep. 
Verify the permissions on the MDBDATA folder. 
Change the properties of the System Attendant Service so it runs in the context of the Local System Account.