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Exchange database is mandatory on UserMailbox

The warning Exchange database is mandatory on UserMailbox is showing in Exchange Admin Center. It’s showing the warning in the details pane after selecting the user in the mailboxes list view. After calling with the user, we can confirm that she can’t log into her mailbox. What is the solution to Exchange database is mandatory on UserMailbox warning?

Database is mandatory on UserMailbox warning

Before we start, it’s good to reproduce the issue. First, let’s see what is happening in the Exchange Admin Center (EAC). After that, we will check the status in Exchange Management Shell (EMS).

Check database is mandatory warning in Exchange Admin Center

Log in to the EAC with administrator privileges. Click recipients in the feature pane and follow with mailboxes in the tabs. Click the user in the list view. In the details pane, we can see the warning: There are multiple warnings. Click here to see more.

Click on the yellow warning to see more.

Exchange database is mandatory on UserMailbox multiple warnings

The warning is showing that the user mailbox is corrupted.

Exchange database is mandatory on UserMailbox warning

Warning
The object exoip.local/Users/Administrator has been corrupted or isn’t compatible with Microsoft support requirements, and it’s in an inconsistent state. The following validation errors happened:
Database is mandatory on UserMailbox.

Check database is mandatory warning in Exchange Management Shell

Now that we have seen the warning in EAC. It’s good to check what’s showing in EMS.

We are going to make use of the Get-Mailbox cmdlet and the -Identity parameter.

The same warning is showing. WARNING: The object has been corrupted or isn’t compatible with Microsoft support requirements, and it’s in an inconsistent state. The following validation errors happened: WARNING: Database is mandatory on UserMailbox.

Check HomeMDB attribute in ADSI Edit

Log in to the domain controller and navigate to the Start menu. Open Administrative Tools and start ADSIEdit.

Exchange database is mandatory on UserMailbox ADSI Edit

Once opened, right-click ADSI Edit and click Connect to…

Exchange database is mandatory on UserMailbox ADSI Edit connect to

Select Default naming context and click OK.

Exchange database is mandatory on UserMailbox ADSI Edit default naming context

Expand the OU where the user object is configured. In my example, the user is onfigured in the OU=Sales. Right-click the user and click Properties.

Exchange database is mandatory on UserMailbox ADSI Edit user properties

In the Attribute Editor tab, search for attribute homeMDB. We can see that the value is <not set>.

Exchange database is mandatory on UserMailbox HomeMDB value not set

A mailbox that is configured in Exchange Server, needs to have a homeMDB. This attribute contains the mailbox database where the object will be assigned a mailbox (e-mail account).

Solution to Exchange database is mandatory on UserMailbox

Have a look at the mailboxes in EAC. Make sure that you select a user mailbox that does not have the database is mandatory on UserMailbox warning. After you find a user, the next step is to find the user in ADSI Edit.

Right-click the user object that you searched for in the previous step. Again, this user does not have that warning. Search for homeMDB and double-click it.

Exchange database is mandatory on UserMailbox HomeMDB other user

Copy the Value and click twice on OK.

Exchange database is mandatory on UserMailbox copy value

Go to the user object with the <not set> value. That’s the user with the warning. Right-click and click Properties.

Search for HomeMDB and double-click on it.

Paste the copied value. Click OK.

Exchange database is mandatory on UserMailbox set value

Confirm that the value is set. Click OK.

For the changes to take effect, we need to wait a couple of hours. We can force that by restarting the Exchange Information Store.

If there are mailboxes configured on other mailbox databases in the same Exchange Server, restart the service after working hours. All the users that have their mailbox on the effected databases will lose their Outlook Connection for a short moment. If the Exchange Server is configured in a DAG, you can perform a server switchover and restart the service.

Start Windows Services and select Microsoft Exchange Information Store. Click Restart the service.

Verify the results

Verify the results in both EAC and EMS.

Log into EAC and click the mailbox in the list view. There is no warning anymore in the details pane.

Exchange database is mandatory on UserMailbox verify result

Run the cmdlet to check in which database the user mailbox is configured.

It’s looking great. The user can now log into her mailbox account.

Did it help you to fix the warning Exchange database is mandatory on UserMailbox warning?

Conclusion

In this article, you learned about Exchange database is mandatory on UserMailbox warning. The solution to this warning is to have a look in ADSI Edit. In ADSI Edit verify that the homeMDB attribute value is not set for the user object. Copy the homeMDB attribute value of another user object. After that, paste the value in the user object with the warning. Restart the Exchange Information Store service for changes to take effect. As of last, verify the results in both Exchange Admin Center and in Exchange Management Shell.

If you liked this article, you may also like to read Delete mailbox database Exchange 2016. Follow us on Twitter and LinkedIn to stay up to date with the latest articles.

ALI TAJRAN

ALI TAJRAN

ALI TAJRAN is a passionate IT Architect, IT Consultant, and Microsoft Certified Trainer. He started Information Technology at a very young age, and his goal is to teach and inspire others. Read more »

This Post Has 3 Comments

  1. Hi,
    Thanks for all of your articles, I’m learning a lot and clarity about exchange.
    About this topic I have a question about that, I have two Mailboxes, one is SystemMailbox{C1CDB383-C0CC-428B-A1D2-E1DF2A78879C}@xxx.es with Mailbox Type inherited and they present the error that you has mentioned in this article.
    I think those mailboxes exists since the exchange 2010 to 2016 migration.
    ¿What type of mailboxes are those and if it’s secure to delete them?
    Best regards

    1. Hi there,

      I am glad that you are learning a lot from my articles. Knowledge is power.

      I recommend you to follow these articles to have a better understanding of the system mailboxes:

      1. Check Exchange arbitration mailboxes
      2. Move arbitration mailboxes in Exchange Server
      3. Recreate arbitration mailboxes in Exchange Server

      The one you mentioned is a Mailbox database system mailbox. I explained that in the article “Check Exchange Arbitration mailboxes.” You can delete it, and it will recreate if you dismount and mount the mailbox database.

  2. Hi,

    Thank you very much for very good explanation.
    I had the exact problem and I solved it by your instruction.

    Best Regards.

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