How to Fix Error “Cannot open mailbox /o=First Organization /ou=Exchange Administrative Group”?

Summary: The error ‘Cannot open mailbox /o=First Organization /ou=Exchange Administrative Group’ occurs when you try to open the Add-Ins section under Organization in Exchange Admin center (EAC). This may occur when database(s) is dismounted due to corruption or critical Exchange service(s) are either not running or stopped due to a problem with the Exchange server. In this guide, we help you troubleshoot the error and fix database corruption by using an Exchange recovery tool, such as Stellar Repair for Exchange.

How to Fix Error “Cannot open mailbox /o=First Organization /ou=Exchange Administrative Group”?

Exchange Server works like a charm with all the functionalities and opportunities it provides. One of the features of Exchange Server is its ability to push add-ins for Outlook users. These add-ins extend the abilities of the Outlook client with the addition of information and tools, which are compatible with Outlook. As we all know, add-ins are third-party applications that add value to the application. These can be installed from a URL, file, or the Office store.

In our Exchange Server infrastructure, we would not want to allow our users to install any incorrect third-party add-in, which would hinder the communication or operability of Outlook. As admins, we would prefer to have a streamlined system where the users have all the tools they need for collaboration and control the installation. This can be done from the Exchange Admin Center (EAC). This gives us the roles and helps us control the users’ ability to install these add-ins. To do so, we need to click Organization and click on Add-ins.

click Organization and click on Add-ins

From here we can add, remove, and control the add-ins to install. However, sometimes, an error occurs while accessing the add-ins tab.

error occurs while accessing the add-ins tab

The error message reads as:

“Cannot open mailbox /o=My Organization/ou=Exchange Administrative Group (GUI)/cn=Configuration/cn=Servers/cn=EX01/cn=Microsoft System Attendant.”

What are the things we would need to do to troubleshoot the issue?

First, we need to check that all services of our Exchange Server are running and make sure that any service, which is set to automatic start, is started.

The next step is to check if the databases in our Exchange server are all mounted and healthy. This can be done by opening the Exchange Admin Center (EAC) and then clicking on Servers and Databases.

Exchange Admin Center (EAC)

Now, we need to make sure that the status of all databases is set to ‘Mounted’. If one or more databases are not mounted, we need to investigate the matter.

For this, the first thing to do is to check that the server and the drive, where the databases and logs are stored, have ample space. This is one of the major reasons why a database is not mounted and the primary cause of possible corruption in Exchange database or logs.

Next, we need to check the license version of the Exchange Server installed, against the number of databases that are configured. The Exchange Server Standard version allows up to 5 online databases. This means that if you have more than 5 databases, only 5 will be online and the rest will be dismounted. Normally, this would not happen as the Exchange Administrator has control on the number of databases to be configured. But if someone else would have created new databases for testing or any other reason, the extra databases will be dismounted. The only solution for this is to either delete the extra databases or purchase an Exchange Server Enterprise license, which is quite expensive for medium-size business.

If you would have data in the extra database, you need to use the New-MailboxExportRequest to export all the mailboxes and other information from it. If there are Public Folders in the database, then it is a little bit more complicated as you need to use scripts to extract the data or use Outlook.

Another thing to check is if a new application has been installed on the server or any upgrade to the current server applications has been done. Usually, when an application is not compatible with Exchange Server, it can hinder the operations and even corrupt the data. The usual suspects are antivirus and backup software. If the applications are not compatible or Exchange Server friendly, these can clash with the operations and block files.

Another reason would be corruption in the Exchange Server databases due to software issues or hardware failures, such as a faulty motherboard, sudden loss of power, or a bad patch installation. If the database is not safely dismounted, this can be a reason why the database or log gets corrupted.

To start off, we need to use the EseUtil to identify the state of the offline database.

We need to open the Exchange Management Shell (EMS) in our Exchange Server and type the following command to see the state of the database.

eseutil /MH <edb file path>

eseutil /MH <edb file path>

If the database State is in Clean Shutdown, we can simply mount the database. But if the database is failing to mount due to corruption or missing log file, the State will be shown as Dirty Shutdown.

We can repair the database by performing the soft recovery or the hard recovery.

First, we would run the soft recovery, which is a quick repair for databases with minor corruption. When we run the /MH parameter, we also need to notice the line which says Log Required as it will tell about the missing logs. An example of the line is as follows:

Log Required: 4-4 (0x4-0x4)

Now, depending on the level of corruption and the size of database, this will take some time. The soft recovery can be executed using the eseutil/r parameter (as given below).

EseUtil /r E04 /l “M:\mbx01\logs” /d “M:\mbx01\mbx01.edb”

EseUtil /r E04 /l

This will run a quick repair of the database. Once done, we can re-run the EseUtil with the /MH parameter and check the State of the database. If the database is still in the Dirty Shutdown State, we need to do the hard recovery using the /P parameter.

A word of caution about this is that use hard recovery as the last resort as it will purge any data which is deemed as corrupted and there is no guarantee that after running this command the database will become healthy.

As soon as we run the command, it asks to confirm that you accept data loss.

ask to confirm

Alternatively, to avoid hassles and lengthy process, use Stellar Repair for Exchange. This application can open any corrupted Exchange Server database. It extracts data from EDB and saves it to PST and other formats. Additionally, it allows to export recovered EDB data directly to another Exchange Server database or Office 365, thus solving the problem with less effort and in much less time.

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