How to deal with an existing mailbox in Exchange Online (due to Teams being used) before migrating

Brass Contributor

We have a scenario where Teams being used across the organization with a cloud identity. These accounts were recently consolidated with On-premises by soft matching via Entra ID Connect Sync. 


The issue now is, due to Teams were used with the cloud identity before account consolidation, there's a Exchange Online Mailbox for every user. We now have to migrate on-premises mailboxes to EXO as we've deployed Exchange Hybrid. 


My question is, how do we deal with this existing EXO mailbox ? what is the best practice to avoid potential issues to Teams and its data associated with the existing mailbox ?


I really appreciate your thoughts !


Thank you

1 Reply


I don't know if it answers your question precisely, but this Exchange OnPremises to Exchange Online migration tool can migrate your on-premises mailbox to an existing mailbox in Microsoft 365.

Hope this helps.