A permanent resolve for the Microsoft Exchange Active Directory Error 0x51

Microsoft Exchange administrators get hung up some times when they encounter sudden Exchange Errors. Recently we ran into a similar problem that drove us nuts. We had just recently demoted one of our old domain controllers. For a few days everything worked fine.
But, just recently our Exchange Server 2010 started throwing up error 0x51 while pointing to the demoted domain controller. The whole database would be locked up and mostly a restart would make the problem go away.

What actually happens is that the Exchange Management Console tries to connect to the non-existent DC which was a part of the network sometime back. This would throw up an error message similar to this:

Log Name: Application
Source: MSExchange Configuration Cmdlet – Remote Management
Date: DATE
Event ID: 4
Task Category: General
Level: Error
Keywords: Classic
User: N/A
Computer: COMPUTER NAME
Description: Error: Microsoft.Exchange.Data.Directory.SuitabilityDirectoryException: An Active Directory error 0x51 occurred when trying to check the suitability of server ‘SERVER NAME’. Error: ‘Active directory response: The LDAP server is unavailable.’

What we found online was that the aforestated error is a result of Exchange Management Console trying to connect to an old domain controller that is no longer available. To point to the new domain controller we had to follow these steps:

• Open Exchange Management Console
• Right click on Organization Configuration
• Click Modify Configuration Domain Controller
• Check Use Default Domain Controller

This should have resolved the issue. However, we were able to execute the same steps successfully but the problem persisted. We tried another solution that was to delete the Exchange Management Console file from the following location:

C:\users\\AppData\Roaming\Microsoft\MMC\Exchange Management Console

Close and restart Exchange Management Console. But the issue still lingered on and there was no other way but to opt for a third party Exchange Server Recovery tool. Stellar Phoenix Mailbox Exchange Server Recovery is one such powerful solution that can resolve all kinds of Exchange Server Errors, JET Engine errors and Active Directory errors. 

The software can be downloaded from the website and shows a clear preview of the Exchange Mailbox items even in the demo version. You can chose to select which items you need to recover. We downloaded the free trial version and checked the preview. It had all the data we wanted to recover.

We activated the software after purchasing the full license version and easily recovered Exchange database as PST. For all the Exchange users who are facing such critical issues where the database is at stake, they can rely on Stellar. Visit tool - http://exchange.stellarservertools.com/