Today I was asked to look at an Exchange 2010 server where the New Certificate Wizard wouldn’t run.

When the wizard was launched from the Action Pane in the Exchange Management Console the following error was presented:

Microsoft Corporation
Microsoft® Windows® Operating System

Object reference not set to an instance of an object.
System.NullReferenceException: Object reference not set to an instance of an object.  at Microsoft.Exchange.Management.SnapIn.Esm.Servers.NewCertificateBestPractice.DefaultDomainNamesGenerator. GetE14Servers(MonadConnection connection)

After a bit of investigating I was able to determin the reason for this was bacause of a failed or partially installed/removed Exchange Server existing in the organisation.

To check this using ADSI Edit.  From Start > Administrative Tools launch ADSI Edit.

Right click on ADSI Edit when launched and select Connect to and then select Configuration as per the image below.

Then click OK, expand Configuration > Configuration > Services > Microsoft Exchange > Organisation Name > Administrative Groups > Exchange Administrative Group > Servers.  As per image below

Make sure that all the servers listed here are part of your Exchange Organisation, if they are not then if possible uninstall Exchange from them.  If uninstalling is not possible then you will need to select the Exchange Server from this location in ADSI Edit, right click and select delete.

Please take caution when deleting items from ADSI Edit.  And only perform this task if absolutely necessary.

Once this has been completed restart the Exchange Management Console and you will now be able to complete the task you were trying to perform when the error was generated.

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