In Exchange Server, a mailbox database is either in the ‘Mounted’ or ‘Dismounted’ state. When the mailbox database is mounted, users whose mailboxes are in the database can access their emails and send or receive new messages. On the contrary, mailboxes in a dismounted database are inaccessible and users cannot access their mail items. However, when the mailbox database status is displayed as ‘Unknown’, it indicates a problem with the mailbox database. Unknown database status in Exchange Server is a sign of an unhealthy or damaged database.
Sometimes, you also notice that even though the database is mounted, the Content Index State is ‘Unknown’ or ‘Not Available’.
Although users can access their mailboxes from mailbox databases with ‘Unknown’ status, it affects the email delivery. The emails sent or received are queued for an extended period and may take from a few minutes to several hours to process and deliver. However, when the database is severely damaged, users may fail to access their accounts and mailboxes.
This can have adverse effects on the workflow and productivity of any organization. Thus, it is critical to resolving the Unknown database status error as soon as possible. Below, we have discussed the reasons behind this error and troubleshooting steps to resolve the database status ‘unknown’ in Exchange. Also, steps to repair the damaged database using EseUtil and Exchange recovery software.
We, recommend checking out Stellar Exchange Toolkit, An advanced tool for Exchange database administrators.
Reasons for Exchange Database Status ‘Unknown’
There are several reasons that can lead to an unhealthy Exchange database with an ‘Unknown’ status. Some of them are as follows:
- Inconsistent, damaged, or corrupt Exchange database
- Renaming Exchange database
- Critical Microsoft Exchange Services
Steps to Fix Database Status Unknown in Exchange
Database status unknown error may occur in both Standalone Exchange Server and DAG environment. However, when it happens in a DAG environment, automatic failover protection (database recovery) comes into action. The member server with a healthy copy replaces the damaged one automatically. Thus, users never notice any glitch.
However, in a standalone environment, there is no failover protection or automatic database recovery. Thus, users experience glitches and errors while accessing their mailbox and sending or receiving new emails.
To resolve this, follow these steps:
Step 1: Restart the Server
A simple restart sometimes can do magic. It can resolve from the most nominal to dreadful errors in a few minutes. So, perform a simple restart and then check the database status.
Most probably, the ‘Status’ should change to ‘Mounted.’ If not, follow the next steps.
Step 2: Restart Exchange Services
Sometimes, critical Exchange Services may stop or need restarting to fix the database status Unknown issue. Follow these steps to start/restart Exchange Services:
- Press Windows + R and type msc.
- Press ‘Enter’ or click ‘’
Step 3: Remount Database
You may try to dismount and then mount the database to fix the database status Unknown error. The steps are as follows:
- Open Exchange Management Shell (EMS) as administrator.
- Check the database status using the following command,
Get-MailboxDatabase –Status | Ft Name, Server, Mounted
Although the Mounted status is shown as True in the output, the database Status will be displayed as Unknown when you check it in the Exchange Administrative Center (EAC).
- Note the database name with Unknown state and then run the following command to dismount it.
Dismount-Database –Identity “DatabaseName”
Dismount-Database –Identity “MBXDB01”
Press ‘a’ and then hit the ‘Enter’ key.
- Then mount the database using the following command,
Mount-Database –Identity “MBXDB01”
Open Exchange Management Shell and check if the database status has changed from Unknown to Mounted.
If the database does not dismount or the mailbox database mount fails, you need to repair and recover the Exchange database.
Step 4: Repair the Exchange Database
To repair the Exchange database with ‘Unknown’ status, you can use the Extensible Storage Engine Utilities (EseUtil). Follow the steps to perform Soft Recovery on the database.
Note: Dismount the database with Unknown status before running the EseUtil commands for database repair and recovery. If the database does not dismount, use the New-MailboxRepairRequest cmdlet to repair the database.
- Open Exchange Management Shell (EMS) and run the following command,
ESEUTIL /r <log_prefix> /l <path_to_the_folder_with_log_files> /d <path_to_the_folder_with_the_database>
Eseutil /r E00 /l ‘PathToLogFolder’ /d ‘PathToDatabasefolder’
- If Soft Recovery fails, you may also attempt Hard Recovery by using the following command,
Eseutil /p “PathToDatabaseFile/Databasename.edb”
However, Hard Recovery may lead to data loss as it purges irrecoverable mail items and mailboxes during recovery.
To avoid the risk of data loss, use Exchange recovery software, such as Stellar Repair for Exchange. Instead of running hard recovery, you can use the software to extract mailboxes from the database and export them to a healthy database directly. It automatically maps the source and destination mailboxes.
It can export up to four mailboxes simultaneously from your inconsistent or corrupt database to a new or healthy database on any live Exchange Server or Office 365 in a few clicks. You can download the free demo to get started.
Database status ‘Unknown’ indicates a problem with the mailbox database and should be addressed promptly. It not only disrupts the email flow but may also result in a data loss situation if not fixed. In most cases, a database with unknown status cannot be dismounted. Thus, the only options you have are to check Exchange services and repair the Exchange database using EseUtil or Exchange recovery software. You can follow the steps discussed in this blog to troubleshoot and fix database status Unknown in Exchange 2010, 2013, 2016, or 2019.