After moving several users successful from Exchange 2013 on-premises to Office 365 at one point the migrated stopped (for some users) with the following error message: “You can’t use the domain because it’s not an accepted domain for your organization”:

PS C:\Windows\system32> New-MoveRequest -Identity j.doe @contoso.com –remote -RemoteHostName webmail.contoso.com -RemoteCredential $RemoteCred –TargetDelivery Domain ‘contosonl.mail.onmicrosoft.com’ -BadItemLimit 10

WARNING: When an item can’t be read from the source database or it can’t be written to the destination database, it will be considered corrupted. By specifying a non-zero BadItemLimit, you are requesting Exchange not copy such items to the destination mailbox. At move completion, these corrupted items will not be available at the destination mailbox.

You can’t use the domain because it’s not an accepted domain for your organization.

+ CategoryInfo : NotSpecified: (:) [New-MoveRequest], NotAccepted

DomainException

+ FullyQualifiedErrorId : [Server=AM2PR01MB0658,RequestId=ea6b71b2-cbb2-4ae8-b57c-f3a2c7fd3bf0,TimeStamp=6-9-2014 11:31:08] [FailureCategory=Cmdlet-NotAcceptedDomainException] B7CD6F09,Microsoft.Exchange.Management.RecipientTasks.NewMoveRequest

+ PSComputerName : outlook.office365.com

PS C:\Windows\system32>

At first I thought the issue was with the TargetDeliveryDomain, but this didn’t make sense since it is identical for all users. The primary SMTP address for the user was also not an issue.

After some digging around in the Exchange 2013 on-premises environment it turned out that some users still had some email address from an earlier (interforest) Exchange migration. Email addresses that were not in use anymore, and therefore not created as Accepted Domains in Office 365.

Removed these email addresses from the Mailboxes causing issues and it worked again.