Using EOP to hold incoming mail

Don 41 Reputation points
2022-03-22T05:01:35.333+00:00

I am planning a migration where we will be moving mailboxes from one tenant to another. We will also be moving the domain that these mailboxes use. We plan to do a cutover migration over an agreed outage period (which includes stripping the UPN & proxyaddresses from objects in the source tenant, moving the domain, adding back UPN & proxyaddresses in the target tenant).

My question relates to using a service to hold all incoming mail during this outage period. I'm aware that most mail systems will defer the delivery of mail if it is unable to deliver it, which in Exchange Online Protection is up to 24 hours. As this outage period may take longer than many deferral periods, we need a service that can hold new mail up until we are ready to release it.

I'm not aware of EOP having the ability to do this; is anyone aware of whether EOP has the ability for an admin to manually put a domain on hold? The path we are looking at is to use a cloud-based mail filtering solution that offers this service. Can anyone recommend of a service that offers this? I'd also like to know if there are other ways to manage this that I haven't yet considered. Thanks for reading my question.

Windows 365 Enterprise
Windows 365 Business
Exchange Server Management
Exchange Server Management
Exchange Server: A family of Microsoft client/server messaging and collaboration software.Management: The act or process of organizing, handling, directing or controlling something.
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Accepted answer
  1. Andy David - MVP 144.4K Reputation points MVP
    2022-03-22T11:10:50.753+00:00

    There are a number of services that do this ( Mimecast etc...) but all will cost of course and it means changing your mx record.

    Me? I would create a transport rule at the very top that quarantines all messages and stop processing rules.
    By default EOP will hold for 14 days.

    185614-image.png

    Then when done, release everything quarantined during that time. You may release some SPAM, but at least you will have the mail.

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