Question Regarding Rebranding Initiative and Radar...

Recently we had to switch a customer primary SMTP domain from to due to legal ramification.  This particular customer is running in a Hybrid mode Office 365 scenario with Exchange and AD On-Prem and in this case that business unit is fully migrated to the cloud.  In other words, they show up as remote recipients under Contacts on-prem Exchange not Mailboxes.

First of all, despite ADFS none of the addresses updated on Reflexion so I was forced to bulk import the new ID's.  Same issue on Radar but support did something not I.  And don't want to know.

The rebranding initiative was difficult enough and we have a mandate to on day X we cannot receive mail to the "Inbox" of the recipient but the customer in this case negotiated keeping the domain name and DNS management and so forth until end of year.  They did that so they could change websites, send out notifications, and all those old emails and addresses it only takes one reply click to send that email back to domain.  I have Reflexion pointing at 365 for this domain with full archiving and DR.

The old domain is now secondary SMTP.  Per the customer request we need to except mail from but drop it and respond with a basic message that says "hey, change your domain to and resend it...."

Simple enough with a Transport Rule.  Well, not so much on Office 365.  You have no ability to modify the generic style NDR messages that go back and in this case the "Tenant" domain is not this domain because there are 56 domains under one tenant.  

So I can create a basic transport rule that blocks the mail and sends a basic message back to the sender and even created a message to the intended recipient with the basics of the email such as to line and subject.

Yet the secondary domain still resides on Reflexion.  And that means it will get archived regardless.

I don't see a way to except one domain from archiving but then again I've been awake for 3 days now.

It sounds like I need to remove from Reflexion and change MX records to point direct and Office 365.

Not sure I have any other choice.

I cannot claim no mail will get delivered only for someone to login to Radar and find it.