Exchange Online Auto-Archiving: 96% Mailbox Quota Trigger, PowerShell Controls and GCC Rollout

One number in that roadmap entry needs correcting. It says the trigger is 95% of quota. Microsoft's technical documentation says something different, and admins should plan around the documentation.

The headline correction: 96%, not 95%​

Microsoft Learn says the feature exists to prevent disruptions in mail flow when a user's mailbox exceeds 96% of its quota. The Exchange team's Tech Community announcement uses the same number. It says that when usage exceeds 96% of its quota and archive mailbox is present, this feature automatically moves the oldest items excluding those tagged with "Never Move to Archive".

Earlier versions used a different figure as well. AdminDroid's write-up mentions an increased trigger threshold from 90% to 96%, so the default has already changed once during the preview. If your runbooks or user guidance say 95% because they were copied from the roadmap, change them to 96%. Better still, check what your own tenant is set to, because the threshold can be changed (details below).

Section summary: The default trigger is 96% of quota. The roadmap's 95% does not match Microsoft's documentation.

What Auto-Archiving actually does​

Microsoft calls this threshold-based archiving that complements existing time-based archiving policies. Your existing retention tags and MRM policies still move mail based on its age. Auto-Archiving adds a second rule that moves mail when the mailbox is nearly full.

The work is done by the Managed Folder Assistant (MFA), the same background process that already handles retention tags. According to Microsoft Learn:

• MFA continuously monitors the primary mailbox size, and archives the oldest items first until usage falls below the threshold, as long as an archive exists and has space.
• The same logic covers Recoverable Items folders (the "Dumpster") when they approach their own quota. The two areas are checked separately. If the Recoverable Items area is over 96%, its older items are archived. If the visible folders are over 96%, older items there are archived.
• Each run tries to move 3% of the relevant quota. Microsoft's example: with a 100 GB ProhibitSendReceiveQuota or RecoverableItemsQuota, a run tries to move 3 GB.
• Mail received in the last 60 days is never auto-archived. Under Top of Information Store, "oldest" is based on received date.
• Archived items go into the user's Online Archive tree with the same folder structure, and they stay accessible and searchable.

Microsoft does not say how often MFA runs, and it does not promise that one pass will bring a mailbox back under the threshold.

What it won't touch​

Not all item types are eligible. Microsoft's FAQ says all item classes are supported except IPM.Appointment, IPM.AppointmentSeries, IPM.Task, IPM.Contact, IPM.DistList, IPM.File and IPM.File.Document. Calendar items, tasks and contacts stay where they are. Any item or folder tagged Never Move to Archive is also skipped.

Section summary: MFA moves the oldest eligible mail, about 3% of quota per run, from whichever area is over the threshold. It skips mail newer than 60 days, calendar, contacts, tasks and anything tagged Never Move to Archive.

What it doesn't do​

The scope of this feature is narrow, and three things are often assumed that aren't true:

1. It doesn't create archives. Microsoft says This feature is called Auto-Archiving, which is different from Auto expanding Archive. The archive mailbox has to be provisioned already and needs free space. Exchange Online must also be enabled for the user, except when RecipientTypeDetails is SharedMailbox.
2. It doesn't turn on auto-expanding archives. If the main archive is full and auto-expanding archiving isn't enabled, Auto-Archiving stops moving items. Once that happens, the mailbox fills up as it would have before.
3. It doesn't change retention. Microsoft's documentation says Auto-archiving temporarily overrides existing archiving policies when triggered. The feature doesn't change deletion or retention policies. The FAQ also says it runs on mailboxes under retention hold, keeping mail flowing without breaking compliance. No default archiving policy is needed. A provisioned archive is enough.

Moving mail between a user's primary mailbox and archive is a storage change. It is not a records-management decision.

Admin controls: the PowerShell you'll need​

The feature is on by default for each mailbox. Merill Fernando's Message Center tracker shows the change was announced as MC1191923, which says it is Enabled by default for all tenants. Most tenants can leave it alone. These are the documented controls, run from Exchange Online PowerShell:

Turn it off for one mailbox:

Set-Mailbox <user mailbox> -AutoArchivingEnabled $false

Change the tenant-wide threshold (example: 90%):

Set-OrganizationConfig -AutoArchivingThresholdPercentage 90

The default is 96 and valid values are 80 to 100. There is no separate organization-wide on/off switch. Setting the threshold to 100 disables the feature for the whole tenant.

Check what happened on a specific mailbox:

Export-MailboxDiagnosticLogs -Identity <user mailbox> -ComponentName MRM

Microsoft's sample output includes a completion entry, the "items archived till date" cutoff, the total items and bytes archived, and a line saying the run started because utilization crossed the threshold. If a user asks where their old mail went, start here.

A field report worth knowing about​

Not every early report has been smooth. In a January 2026 comment on LazyAdmin's explainer, an admin wrote that some of our users that triggered the auto-archiving had EVERY messaged in their inbox moved into the online archive after their mailbox passed the 96% threshold. Their diagnostic log showed a run that tried to move 3 GB, and the commenter questioned that figure on an F3 mailbox. This is one unverified user report, not a confirmed bug. Microsoft's documentation does say each run targets 3% of ProhibitSendReceiveQuota or RecoverableItemsQuota, so the per-run amount depends on the quota value MFA reads. Before you roll this out to small-quota users such as frontline staff, run Export-MailboxDiagnosticLogs on a pilot mailbox. Compare the "triggered to move" figure with the quota you expect.

Rollout checklist​

The documentation points to the following order of work:

1. List archive coverage. Users without a provisioned archive get nothing from this feature. Decide whether they should have one.
2. Plan archive capacity. For mailboxes with large archives, decide whether auto-expanding archiving should be on. Without it, a full archive stops Auto-Archiving.
3. Check licensing. Microsoft says licensing is the same as for time-based archiving and refers to its Microsoft 365 security and compliance licensing guidance. Check that guidance for your plans instead of assuming.
4. Review Never Move to Archive tags. Anything that must stay in the primary mailbox, for example because of offline access or a third-party tool, needs the tag.
5. Pick a threshold. Keep 96, lower it as far as 80 for more headroom, or set 100 to opt the tenant out.
6. Tell the help desk. The Message Center post advises admins to Review internal documentation and communicate this change to helpdesk staff. Users who find mail moved to "Online Archive" will call. A short script for the help desk saves time.
7. Watch the MRM diagnostics on a few pilot mailboxes before you rely on it widely.

Government clouds and timing​

Microsoft Learn says the feature entered public preview in November 2025 after a private preview for selected customers. The Tech Community post gives a preview start of November 15, 2025. The admin roadmap aggregator HandsOnTek, quoting the Message Center post, said the Rollout starts January 2026.

The roadmap item covered here lists GCC, GCC High and DoD, with GA in February 2026 and status "Launched". Our capture of the roadmap page did not show those per-item details, so the cloud list and GA date come from the roadmap metadata only. Microsoft's roadmap also says its dates are estimates and subject to change. Government-cloud admins should confirm availability in their own tenant, for example by checking whether Get-OrganizationConfig returns an AutoArchivingThresholdPercentage value.

Analysis: a useful safety net with limits​

Auto-Archiving reacts to a nearly full mailbox instead of waiting for a fixed age. That matters because time-based archiving only moves mail once it reaches a set age. A burst of large attachments, a busy shared mailbox or a growing Recoverable Items folder (common on mailboxes under hold) can fill the primary mailbox well before then.

It does not create space. It only moves mail into whatever archive space you have already given the user. If you haven't provisioned archives, haven't planned archive capacity, or haven't used the Never Move to Archive tag where needed, the feature either does nothing or moves mail you would rather have kept in the primary mailbox. It also runs automatically, which means a user may see an empty inbox before the help desk knows why.

For most tenants the default setting is reasonable. Before relying on it, confirm that users have archives with space and that your documentation says 96%, not the roadmap's 95%.