T2T migration

I am trying to determine if ODM can meet the following requirements for an O365 T2T migration and would appreciate any help/guidance.  Company A is acquiring Company B, Company A is larger than Company B, however, Company A would like to start sending mail with Company B's smtp namespace as soon as possible.  From what I am reading it seems that ODM can handle that task for users that are migrated from Company B's tenant to Company A's tenant.  If we utilize the address redirection piece will it require an ODM license for the objects that exist in Company A currently?  I am still thinking about the implications of DirSync from Company A to O365 and how we bring the objects under control once, if we even need to at this time.

Any guidance or lessons learned will be appreciated,



  • Could you not just create a Contact in the Company B tenant for each Company A user to be left in place until such time as the MX record for Company B is swung over to the Company A tenant?

  • Hello Luis,


    Thanks for posting to the On Demand Migration (ODM) forum. I understand you have questions about using the ODM Domain Coexistence feature. I understand that in your described scenario, Company A would like to start sending mail with Company B's SMTP namespace as soon as possible. I have a few questions for additional clarity:


    1.) Is the end goal that Company B going to be migrated into Company A's Office 365 tenant?


    2.) Are there existing users in Company A (not migrated) who also want to use Company B's SMTP namespace immediately? If so, roughly how many users?


    3.) In regards to your question about bringing Company B's objects under control of Company A, does Company B have local Active Directory and DirSync?




    Trevor Taegder

    Senior Technical Support Engineer

    Quest | Support