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Users able to reply after migration

Hi guys,

So we are about to migrate a small group of mailboxes from one tenant to another and my question is if the users can reply to migrated emails when the logon to the new tenant?

From what I can remember back in the days (or might still be applicable) one have to do something with the X500 protocol or ExchangeLegacyDN?


1) Do we need to do something on the target mailboxes so they are able to reply to migrated email?

2) What is needed to be changed/added?

3) Is this applicable even if the source tenant are only cloud-ids and have not been migrated mailboxes from an on-premises enivronment.


  • Thanks for posting in the On Demand Migration for Email (ODME) community forum. I understand you have questions about an upcoming Office 365 tenant to Office 365 tenant migration.

    1.) Typically, there is nothing that needs to be done on the target mailboxes so that they can reply to migrated email.

    2.) Typically, there is nothing that needs to be changed or added. You will just need to create mailboxes in the target.

    3.) Typically, this should not change the migration scenario.

    Note: I have heard of one particular instance where a customer needed to copy the LegacyExchangeDn from the source mailbox onto the proxyAddresses in the target (as an x500 address) in order for a particular user to be able to update migrated meetings. However, I believe this was a one-off and I did not have enough information to determine the cause that required this workaround.

    I also want to point out that we have recently released a new On Demand Migration product, which is specifically designed to perform Office 365 tenant to Office 365 tenant migrations. On Demand Migration provides additional functionality for tenant to tenant migrations, including creating and licensing target mailboxes and migrating OneDrive. You can find out more here:

    Please let me know if you have any additional questions or need any additional clarification. 


    Trevor Taegder
    Senior Technical Support Engineer

    Quest | Support