"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."

This event generally occurs when the Exchange mailbox store fails to mount or if you have stopped the Information store service. There could also be a possible corruption in the Information store.

"Operation terminated with error -1601 (JET_errRecordNotFound, The key was not found) after 2.354 seconds."

This error occurs when you try to perform database repair against the .stm file. This operation damages the internal structure of the file and generates the above error.

"Operation terminated with error -1601 (JET_errRecordNotFound, The key was not found) after 2.354 seconds."

This error occurs when you try to perform database repair against the .stm file. This operation damages the internal structure of the file and generates the above error.

"Operation terminated with error -1605 (JET_errKeyDuplicate, Illegal duplicate key) after xxx.xxx seconds."

You will see this error message after a premature exit of Eseutil /P while performing EDB database repair. This situation usually arises when the Eseutil tool rebuilds B-trees incorrectly.

"JET_errReadVerifyFailure Read verification error 4294966278"

There are various reasons that can trigger this error. There may be some bad sectors on your hard disk or a third-party software integrated with Exchange server has incorrectly written information to the file. Another reason could be corruption in your Exchange database.

"ERROR: database was not shutdown cleanly (dirty shutdown)."

This error occurs when the Information store service is abruptly closed due to a power outage or any other reason. This may cause corruptions in Exchange database '.edb' and '.stm' files.

"JET_errInvalidLogSequence"

The error signals that one of your log files is either missing or does not match other log files in the sequence. This may occur due to an invalid log signature or if the creation time does not relate to other logs in the sequence.

"Unable to initialize the store service. Failed to search for MSEXCHUCE in DS. 0x80004005"

You may encounter this error after you have upgraded to MS Exchange Server 2003 SP2. This generally happens when a time-out occurs during the LDAP query. One of the Domain Controllers might be under a heavy load.

In order to effectively resolve these errors and overcome all issues surrounding Exchange database inaccessibility, use Stellar Repair for Exchange. The software encapsulates powerful mechanisms that are adept at repairing any damaged Exchange database and recovering precious user mailboxes with their exact structure and composition. The tool efficiently handles each case of EDB file corruption to safely restore all your valuable mail items, including email messages, attachments, tasks, contacts, calendars, notes, journals, etc. Moreover, the software is compatible with Windows 7, Vista, Server 2012 and 2008.