"Not a valid SMTP address" error when you migrate mailboxes to Exchange Online in a cutover migration


You're performing a cutover migration to migrate all mailboxes from your on-premises Exchange organization to Exchange Online. The source server for the migration is running Microsoft Exchange Server 2016, Exchange Server 2013, Exchange Server 2010, or Exchange Server 2007. However, the migration attempt fails, and you receive the following error message:
"/o=NT5/ou=###xx##x#x##x###x##xxxx/cn=###xx##x#x##x###x##xxxx" is not a valid SMTP address”


This issue occurs if the migration batch includes invalid or stale global address list (GAL) entries. 


To resolve this issue, follow these steps:
  1. Open Exchange Management Shell on the on-premises Exchange server.
  2. Run the following command:
    Update-GlobalAddressList –Identity “Default Global Address List” –DomainController “NameOfDomainController” 
  3. Delete and then re-create the cutover migration batch in Exchange Online.


Exchange Server 2003 uses the Recipient Update Service, and this creates and maintains Active Directory attribute values. This service is not included in Exchange 2007 and later versions. Therefore, stale or invalid entries can exist on objects in Active Directory Domain Services (AD DS) in Exchange Server 2016, Exchange Server 2013, Exchange Server 2010, and Exchange Server 2007. These entries do not present an issue until you try to migrate and create new cloud objects.

Still need help? Go to Microsoft Community or the Exchange TechNet Forums.

Article ID: 2965789 - Last Review: Dec 28, 2016 - Revision: 1

Microsoft Exchange Online, Exchange Server 2016 Enterprise Edition, Exchange Server 2016 Standard Edition, Microsoft Exchange Server 2013 Enterprise, Microsoft Exchange Server 2013 Standard Edition, Microsoft Exchange Server 2010 Enterprise, Microsoft Exchange Server 2010 Standard, Microsoft Exchange Server 2007 Enterprise Edition, Microsoft Exchange Server 2007 Standard Edition