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We can’t create a mailbox in Exchange Server, and it shows the error: Load balancing failed to find a valid mailbox database. We didn’t change anything, and this error occured. Why is this happening, and what is the solution?

Error: Load balancing failed to find a valid mailbox database

Sign in to Exchange Admin Center and create a new mailbox for the user. The below error shows up:

Load balancing failed to find a valid mailbox database error

error
Load balancing failed to find a valid mailbox database.

Why do we get this error, and what is the solution for load balancing failed to find a valid mailbox database?

Check mailbox database provisioning status

Find the mailbox database values on the objects:

  • IsExcludedFromProvisioning
  • IsSuspendedFromProvisioning

Start Exchange Management Shell as administrator and run the below command.

PS] C:\>Get-MailboxDatabase | Format-List Name,IsExcludedFrom*,IsSuspended*


Name                                                : DB01
IsExcludedFromProvisioning                          : True
IsExcludedFromProvisioningReason                    :
IsExcludedFromProvisioningBy                        :
IsExcludedFromProvisioningBySchemaVersionMonitoring : False
IsExcludedFromInitialProvisioning                   : False
IsExcludedFromProvisioningBySpaceMonitoring         : False
IsExcludedFromProvisioningForDraining               : False
IsExcludedFromProvisioningByOperator                : False
IsExcludedFromProvisioningDueToLogicalCorruption    : False
IsSuspendedFromProvisioning                         : False

Now that we gathered all the information, we can see that one value is True.

Solution for load balancing failed to find a valid mailbox database

You can set the IsExcludedFromProvisioning value to True on the mailbox database. But in our case, this wasn’t set by us. This happened automatically because the mailbox database disk size was full, and there was no more space left. Exchange Server will notice this and exclude the mailbox database from provisioning.

After expanding the disk, the mailbox database will stay excluded, and you have to set the value back to False. Unfortunately, Exchange Server will not do this automatically for you.

Run the below command to set the mailbox database IsExcludedFromProvisioning object value False.

[PS] C:\>Set-MailboxDatabase "DB01" -IsExcludedFromProvisioning $false

After applying the above command, you don’t have to remount the mailbox database or restart any Exchange Server service.

Note: Suppose you see other objects with the value True. Change them to False.

You can now create a user mailbox in the mailbox database without seeing the error: Load balancing failed to find a valid mailbox database.

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