Migration advice

Steel Contributor

Hi all.


Hope everyone is well. I was looking for some advice. We are in the process of a merger and we are getting new Office 365 accounts in the acquiring company’s Office 365 tenant.

I wanted some advice with regards to on-premises mail flow.

Here is my setup:

My AD domain is mycompany.local.

Exchange is 2016 hybrid. All email is in Exchange Online within my current tenant.

I am hosting 6 companies with vanity domain names for each of them.

MX for each company points to EXO and all email, even from on-premises gets sent out via EXO.

4 of the 6 companies I am hosting will move across to the new the tenant.

The domains will be removed from my tenant and added to the new tenant.

The problem I am facing is that I have a lot of on-premises systems that sends email to my mailboxes hosted in EXO.

Each of my users have a remote routing address of:


What is the best way to ensure mail flow from on-premises still flows to my users that will be hosted in the new tenant while still being in a supported scenario with Microsoft?

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