For Exchange Server, MAPI uses different interface methods. The OpenMsgStore is the method associated with IMAPISession interface that is used to open a message store. The method then results a reference that is passed to ImsgStore object for further access. When the method fails, the Application log of Exchange Server computer records an event that you can analyze for knowing the root cause of failure. Amongst other reasons, one possible cause of this behaviour could the corruption of message store. If this is the case, you require to run Eseutil repair utility, restore from backup or apply a mailbox recovery technique. However, you can also use an Exchange Server Recovery product in case none of these solutions seems relevant.

For instance, you may encounter the below event log description displaying in the application event log of Exchange Server computer:

The MAPI call 'OpenMsgStore' failed with the following error:
The Microsoft Exchange Server computer is not available. Either there are network problems or the Microsoft Exchange Server computer is down for maintenance. The MAPI provider failed.
Microsoft Exchange Server Information Store
ID no: 8004011d-0526-00000000

The error is logged with event ID 9175 and is specific to Exchange Server 2000 and 2003.

Cause

The above error indicates that the Information Store (IS) is not running or the mailbox store is failing to mount. If the IS doesn't run, the System Attendant still remains active with the MAPI session. The IS may stop due to any of the below possible reasons:

1. You are using an expired evaluation version of Exchange Server
2. The partition storing the IS files is less than or equal to 10 MB in size
3. The IS is in dirty shutdown state
4. The store is dismounted and/or corrupted

Solution

You should first verify if the IS is running or not. For this, go to Services and check the status of Information Store. If it is running, make sure that the mailbox store(s) are mounted and if it is not running, try to restart the store. You can try these suggestions to overcome the IS and mount failure issues:

1. Use the activated version of Exchange Server
2. Make sure that the IS partition is greater than 10 MB in size
3. Replay all the transaction log files for the affected mailbox store
4. Backup your store and run eseutil /p command to repair it. The command can delete the corrupted pages and cause data loss.

For repairing the corrupted Exchange database safely, it is recommended to use an Exchange Recovery utility. Microsoft Exchange Recovery software are scanning-based products specifically built to repair the corrupted database and restore it at a safe location.

Stellar Phoenix Mailbox Exchange Recovery is an advanced tool that repairs the corrupted Exchange database and extracts mailboxes in individual *.pst files. The powerful Exchange Recovery solution can restore all file objects using safe algorithms. The tool supports Exchange Server 5.5, 2000, and 2003.