BTW, I amended the retention policy for a folder to apply a mailbox retention tag that removed items after a week. I then ran Start-ManagedFolderAssistant and after a short while, all items more than 7 days old were deleted.

I’m afraid that it’s impossible to know what’s happening without access to your tenant data, which I obviously don’t have.

What sources are you citing? It’s entirely possible that things have changed since the article appeared. There have been many changes in the compliance area over the last two years.

Hi. We have since seen some odd behaviour where using both modern and legacy policies in harmony.
Scenario – a) modern m365 policy with 7 x year retention set. b) legacy mrm to move items to archive > 2 yrs c) legacy mrm to remove from deleted items > 30 x days d) legacy mrm remove from junk folder > 30 x days. a and b seem to work fine and as expected. But c and d do not even show as applied tags to users exo mbx’s so we suspect from further sources that the specific legacy policy mrm tags on folders (c, d) lose out against a modern policy where set (a) and do not work / apply?

Thanks for confirming!

There is no way to target individual folders with Microsoft 365 retention policies. You need MRM for that.

However, we specifically use legacy MRM tags to remove items after 30 x days from junk and deleted items. If we want to continue clearing out these folders must we keep these MRM tags, as can’t see how we can target folders in M365 policies?

I address some of these concerns, like the ability of MRM to function at a more granular level within a mailbox, in another article: https://practical365.com/exchange-online-retention-m365-retention/

I believe Graph API access for retention labels is coming. However, it could be that server-side application of labels via the API might be one of the metered APIs that Microsoft loves to introduce, like that for sensitivity labels.

BTW, unlimited archiving is no longer unlimited. Microsoft applied limits some time ago. https://practical365.com/microsoft-caps-exchange-onlines-unlimited-archive/. The 1.5TB limit reported in September 2021 remains the same today https://learn.microsoft.com/office365/servicedescriptions/exchange-online-service-description/exchange-online-limits?WT.mc_id=M365-MVP-9501#storage-limits

1. It’s important to delineate the functional differences between MRM, modern retention policies, and modern retention labels.

Despite the core object in MRM being a “Retention Policy tag,” its only activities are “Delete on this schedule” and “Move to archive.” There’s no actual protection done of content. Modern retention policies have that capability scoped to the mailbox container level but lack the native configuration granularity of MRM because there’s no recognition of folders like MRM. Modern retention policies have no concept of leaf items; only workload containers (mailboxes, teams, SharePoint sites, etc.).

From the leaf object perspective, a close match to MRM might be modern retention labels. They can be applied (in the end-user context) the same as MRM to individual items (folders, messages, calendar items, and the like). However, like their modern retention policy counterparts, they lack the granular, programmatic service-side assignability that MRM policies do.

2. EWS can be used to apply modern retention labels just like it can be used to apply legacy MRM labels. In fact, I demonstrated this here: https://www.undocumented-features.com/2019/08/27/apply-security-compliance-center-retention-labels-to-outlook-folders/. It’s the exact same syntax whether the policy GUID is related to MRM or retention labels. However, public access to EWS is scheduled to be turned off on October 1, 2026, so building a solution that relies on EWS to apply modern retention labels isn’t viable long-term.

Sadly, there are no available Graph cmdlets or endpoints that work with leaf-object application of retention labels. This is a huge gap area and not likely to be ever addressed.

3. You’re spot-on with the Move-to-Archive functionality. There’s nothing in the modern retention policy/label architecture that allows for that feature. It’s not in the roadmap and won’t ever be–which is also disappointing. From an overall content management perspective (with the 100GB limitation for mailboxes and potential for unlimited archiving), it totally makes sense to retain a legacy MRM configuration that allows you to move content from the primary to archive mailboxes on a defined schedule to help avoid hitting that limit.

4. While you *can,* from a technical perspective, implement modern retention policies and labels against shared, room, or equipment mailboxes (as long as you have at least a single Exchange Online P2 or Office 365 E3 license in the tenant), they must have an Exchange Online Plan 2 license or an Exchange Online Archiving license to be compliant with the service terms.

From https://learn.microsoft.com/en-us/purview/archive-mailboxes

Both mailboxes are considered a user’s mailbox for compliance features such as Content search from the Microsoft Purview compliance portal, Microsoft 365 retention, and Litigation Hold.

“1. Items are moved to the archive mailbox after 2 years.
2. For most users, items are deleted after 7 years (2 in mailbox, 5 in archive)rs online archive mailbox”

Question about this and I believe it is answered in your response quoted above but I can’t find any official MS source on it.

Are scenario is going to be similar:
1. Existing MRM policy to archive user mail (EXO) to their online archive mailbox after 1 YEAR
2. We intend to deploy an Adaptive Scope policy to delete all user mail after 2 years

My questions, does the adaptive scope policy targeting the user mailbox for delete after 2 years include their online archive mailbox? I hope that the answer here is yes!