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Since Exchange Server 2013, Microsoft has brought many changes in the structure of Exchange Server environment. Microsoft also introduced Exchange admin center in the same year that can be used to make desirable changes and perform various activities. When you try to upgrade your Exchange Server directly to the latest version available, there may be some errors due to difference in the software architecture. For example, upgrading from Exchange 2007 to 2013 or from Exchange 2010 to 2016 may bring errors. This error is reported when administrators go to the Add-in section in the Exchange admin center (especially in Exchange 2016). Sometimes, Exchange users get this error, and they won’t be able to access their mailboxes in Outlook or Outlook Web Access (OWA).
The error message displayed is:Cannot open mailbox /o=First Organization /ou=Exchange Administrative Group (FYDIBOHF23SPDLT)/cn=Configuration /cn=Server s/cn=MAILBOX01/cn=Microsoft System Attendant
Let’s learn what leads to this error and how to resolve it efficiently without losing your crucial business data.
Reasons for the error: ‘Cannot open mailbox /o=First Organization /ou=Exchange Administrative Group’
The error usually happens when the Exchange mailbox database, especially the default mailbox database, is not mounted. The default mailbox database is very important as it holds critical information. So, one has to keep the first mailbox database mounted. Otherwise, this error may occur. It can occur when some of the required Exchange services are not running.
The error “Cannot open mailbox /o=First Organization /ou=Exchange Administrative Group” appears after some architectural changes were made in the Exchange Server 2010. From this version onwards, the System Attendant Mailbox was removed from the first mailbox database that was created after the Exchange installation. But the directory object was not removed from the configuration partition. In addition to this, Microsoft Exchange System Attendant (Mad.exe) was removed from Exchange 2013. This architectural change is one of the reasons for the appearance of the error. It is noted that the incorrect or missing System Attendant homeMDB attribute is a reason for this error.
Also, this error can be seen when the mailbox database is corrupt or damaged.
How to fix ‘Cannot open mailbox /o=First Organization /ou=Exchange Administrative Group’?
Rebooting the Exchange Server may help to fix the error. However, rebooting the Server is not a viable solution as it causes wastage of precious working hours. So, we need to look into some serious troubleshooting methods for this error.
Mount the Exchange database
Follow the given steps to mount the dismounted database back to the Exchange Server:
Step 1. First, check if the default mailbox database is mounted. If not, mount it and check if the error disappears. Also, ensure that all Exchange services are running.
Step 2. In the Exchange admin center (EAC), go to servers > databases, and check if the default mailbox database is mounted. If not mounted, select the default database, click ellipses, and click Mount.
Step 3. If you have too many databases and some of them remain unmounted, better remove unmounted databases after exporting their data to other databases.
Note: The database may not mount properly if it is in a Dirty Shutdown state. You can check it using the Eseutil utility.
Step 4. To verify this, use the cmdlets in Eseutil:
eseutil /MH < Database location and name >
Step 5. If it shows Dirty Shutdown State, you need to repair the database. You can perform a soft recovery (using Eseutil):
Eseutil /r E0n /l <Log file location> /d <Database location and name>Edit HomeMDB attribute
Modify the homeMDB attribute
You can use ADSIEDIT to check the System Attendant homeMDB attribute. If this value is incorrect or missing, provide the correct value.
Step 1. In ADSIEDIT, locate the path:
CN=Configuration,CN=Services,CN=Microsoft Exchange,CN=<org name>,CN=Administrative Groups,CN=Exchange Administrative Group (FYDIBOHF23SPDLT) ,CN=Servers,CN=<servername<,CN=Microsoft System Attendant Home MDB
Step 2. If the value is incorrect, locate:
CN=Configuration,CN=Services,CN=Microsoft Exchange,CN=,CN=Administrative Groups,CN=Exchange Administrative Group (FYDIBOHF23SPDLT) ,CN=Databases,CN=<DatabaseName>
Step 3. Copy and paste the value to CN=Microsoft System Attendant Home MDB.
Step 4. Finally, reboot the Exchange Server.
Repair the corrupt Exchange database
Finally, you need to check if the Exchange database or log files are corrupt. If they are corrupt, you need to repair them and recover their data. In case of minor corruption issues, you can rely on Eseutil utility to fix the issue.
For a hard repair without backup files, you can use:
eseutil /p <Database Location with name>
Withdraw the third-party add-ins
Third-party add-ins often tends to interfere with the functionality of the Exchange Server mailbox. This means it is quite important to remove the add-ins one after another and simultaneously check if the database works efficiently as you remove them.
Start the Microsoft Exchange Services
Sometimes the Exchange Server is down, the Exchange services stop working and you need to manually start them again. These services provide the administrator with the authority to take actions for a mailbox or a complete database. The Exchange admin can restart them by running services.msc in the run window (Windows key + R).
For the situations when corruption is severe, you need to try professional utilities like Kernel for Exchange Server to export data from corrupt EDB files to a live Exchange Server. This tool repairs even highly corrupted databases and exports data to various destinations like Outlook PST files, live Exchange Server, and Office 365. This is a user-friendly Exchange EDB mailbox recovery tool and supports all versions of Exchange Server, including Exchange 2019.
Conclusion
The error ‘Cannot open mailbox /o=First Organization /ou=Exchange Administrative Group’ can happen due to various reasons, including Exchange database corruption. If this error is due to EDB file corruption, you can try Exchange Server recovery software to fix the issue. Kernel for Exchange Server recovery is the most efficient solution to scan and recover corrupt mailbox items. Use either Standard Scan or Deep Scan to scan the database file and preview the mailbox items in their original structure.
