Compliance Purview Retention policies

Question

I have created a retention policy at https://compliance.microsoft.com/ > Data lifecycle management > Microsoft 365 that should delete emails from a specified mailbox after 6 months. My question is, these mailboxes still have Default MRM Policy assigned to them with the Exchange Admin Centre, do I need to change this to something else? Or will the Compliance Retention Policy overrule anything set in Exchange? Thank you

Answer 1

Yes you need to create manually tag and policy and assign the user because default MRM policy have multiple tags that's why create a separate policy and tag Tag is for time period and policy for action you need perform like delete or archive the mailbox. Thanks if you this is helpful for you than please mark as accept the answer.

Answer 2

You should use the compliance policy and not the MRM policy. They can be used side by side but the recommendation is to only use the Purview policies going forward unless the MRM policy is moving items to the archive (for example) which can not be done with Purview policies https://learn.microsoft.com/en-us/exchange/security-and-compliance/messaging-records-management/default-retention-policy

Answer 3

Hi @Keir Smith ,

My question is, these mailboxes still have Default MRM Policy assigned to them with the Exchange Admin Centre, do I need to change this to something else? Or will the Compliance Retention Policy overrule anything set in Exchange?

If your final goal is to delete items older than 6 months, agree with Andy that you should use the compliance policy only and remove the MRM policy or any other Exchange based retention policy assigned to the mailbox. As aforementioned in the article shared by Andy, the Exchange based MRM policy will work side-by-side with the compliance retention policies and retention labels when both exist. So, it's not that the Compliance policy overrides the Exchange based MRM policy or vice versa. Based on my understanding, both would be taken into consideration when a mailbox is processed by the backend mailbox assistant and basically it would follow the flow below:
Reference: The principles of retention, or what takes precedence?

so assigning a Retention Policy here on the mailbox AS WELL as a compliance policy should do the trick?

If your goal is to retain items for 6 months, assign the compliance policy only would be enough.

What happens if the compliance policy is 6-month delete but the exchange policy is 1-week delete, which policy wins?

Per my understanding, as illustrated in the image above, Exchange policy (1-week delete) wins in this scenario. (Rule 4. Shortest deletion period wins.) All in all, the recommended way is as Andy said, to use EAC based retention to meet your archiving (mailbox) needs and SCC retention for your retention needs.
See: FAQs on Office 365 Retention, Disposal & Archiving

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