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Exchange Team Blog

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Auto-Archiving for Exchange Online

Platinum Contributor

Oct 07, 2025

Update 10/17/2025: We updated the content of this blog post, the timelines and the FAQ to align with customer feedback we received after initial announcement.

TL; DR: A new capability called Auto Archiving for Exchange Online will enter public preview from November 15, 2025 (currently under private preview for selected customers). When a user's mailbox utilization 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” from the primary mailbox to the archive mailbox to prevent mail flow disruptions by keeping usage below the safe threshold of 96% of mailbox quota.

The need for archiving

Users archive their primary Exchange Online mailboxes to avoid hitting mailbox storage limits, ensure uninterrupted email access, and maintain a clean and organized inbox while still retaining older messages for reference. Archiving also supports compliance with regulatory and legal retention requirements enabling seamless access to historical data through archive views in Outlook

Limitations of tag-based archiving (current behavior)

Even when users configure MRM policies like “Move to Archive after 2 years,” they still may encounter mailbox quota full issues because the volume of incoming data especially from large attachments, automated notifications, and AI-generated content (Copilot generated meeting notes, automated/system generated reports) often exceeds expectations. Users assume that archiving will proactively manage mailbox size, but the archive only activates after a fixed age is met. This could allow data to accumulate rapidly and unexpectedly. As a result, mailboxes can reach full capacity before time-based archiving kicks in, leading to functional loss such as inability to send or receive emails directly impacting business continuity and operational efficiency.

Reimagining archiving: adding Auto Archiving to time-based archiving

Responding to requests of customers who emphasized the need for proactive and automated space management that complements existing retention settings, we are rolling out an update designed to prevent mail flow disruption due to misconfigured archiving policies or situations where mailboxes might fill up faster than expected. With this design change, when mailbox utilization exceeds 96% of mailbox quota, the system will start moving batches of the oldest items to archive mailbox until mailbox utilization drops below 96% utilization in both IPM (visible to users) and recoverable items folders (that if archive mailbox is provisioned for the user and has storage capacity remaining). Auto Archiving will target the oldest emails first, moving them into the archive until the primary mailbox usage is safely below the threshold. Auto archiving approach ensures that mailbox usage is brought back below the 96% threshold before users experience functional loss such as inability to send or receive emails ensuring real-time mailbox health monitoring across organizations.

Note: This feature is called Auto-Archiving which is different from Auto expanding Archive.

How it works

The Managed Folder Assistant will continuously monitor the primary mailbox size. As and when primary mailbox size exceeds 96% of the current mailbox quota and provided the archive mailbox is provisioned and has remaining space, Managed Folder Assistant will automatically archive the oldest items first until usage drops below the threshold. The same concept applies to Recoverable Items (“Dumpster”) folders when they are near their quota.

Note: Oldest items in IPM folders are based on received date.

Availability

Public Preview: starting November 15, 2025, enabled for tenants who have opted into Targeted Release option.
General Availability (WW cloud): January 15, 2026 (tentative)
Government clouds roll out: February 15, 2026 (tentative)

We are creating a Microsoft 365 Roadmap item for this feature and plan to send a Message Center post to tenants who the feature will impact, before GA.

FAQs

Q: When will Auto-Archiving get triggered?
A: It will get triggered when user’s primary mailbox has exceeded 96% utilization, the archive mailbox is already provisioned and has remaining storage capacity for items to be archived.

Q: What will happen to our current archiving policy?
A: There is no change in how archiving policy works today. Auto Archiving will only kick in as failsafe once primary mailbox size exceeds 96% threshold of mailbox quota to avoid any mail flow disruptions. Once Auto Archiving gets triggered, it will temporarily override the current archiving policy and move batches of oldest items based on received date till mailbox utilization drops below the threshold.

Q: We have items/folders with the “Never Move to Archive” tag. What will happen to those items once Auto-Archiving kicks in?
A: The “Never Move to Archive” tag will be still honored. That means the Auto Archiving will skip items/folders with “Never Move to Archive” tag.

Q: Will mailbox users notice that something has changed?
A: If their mailbox quota reaches 96%, their oldest mailbox items will move to the “Online Archive –” tree while preserving folder structure; mail remains searchable and accessible.

Q: Will this feature also provision archive mailboxes on behalf of users?
A: No. Auto Archiving will only get triggered if the archive mailbox is already provisioned for the user and hence no Archive mailboxes are provisioned automatically on behalf of users unless they are explicitly enabled.

Q: Our user’s Main Archive is full, and auto-expanding archive is not enabled. Will this feature enable auto expansion of archives on behalf of the user?
A: No. This feature will not enable auto expansion of archives on behalf of the user. If the main archive is full, no items will be moved from primary to the main archive. This might result in mailboxes getting full, thus disrupting mail flow. It is advised that auto expansion is enabled for users manually to avoid this scenario.

Q: An archive mailbox has been provisioned for an account, but there is currently no default archiving policy enabled. Will emails be automatically archived when mailbox utilization exceeds 96%, ensuring the primary mailbox does not reach its storage limit?
A: Yes. With this feature, it is not necessary to implement an archiving policy for managing storage utilization in the primary mailbox if archiving has already been enabled (archive mailbox provisioned). But it is recommended to lower the threshold to 90% for the better experience.

Q: Does this change deletion/retention policies?
A: No. This feature doesn’t change deletion behavior; it only relocates items to the archive to prevent primary mailbox quota lockouts.

Q: A mailbox is under Retention hold. Will Auto Archiving still get triggered?
A: Yes. Auto Archiving will archive items even if Retention hold is enabled.

Q: How do we prevent specific important information from being archived?
A: We recommended to use “Never Move to Archive” Tag to prevent important information from being archived.

Q: Is it possible to get details of Auto-Archiving which automatically manages space for a mailbox?
A: Yes. Detailed diagnostics are published for transparency and auditing which can be accessed from Exchange Online shell for a given user.

Export-MailboxDiagnosticLogs -Identity $user -ComponentName MRM

Sample Log:

<Date>; method: PublishDiagnosticsLog; ... Auto- Archiving completed for mailbox: <MbxGuid>. Items archived till date: <Date>. Total items archived: <ItemCount>, Total bytes archived: <Size>. Auto-Archiving was triggered to move <xyz GB> of data because mailbox utilization crossed 96%.

Q: ELC processing is disabled for the mailbox. Will auto archiving still happen for the mailbox?
A: No. Auto archiving will only get triggered if ELC is enabled on the mailbox.

Q: Is it possible to disable Auto-Archiving per mailbox or per tenant?
A: If mailbox size is less than the Auto Archiving threshold percentage (default value is 96%), items will not be archived. Auto Archiving can be turned off for individual mailboxes using the following PowerShell command:

Set-Mailbox <user-smtp-address> -AutoArchivingEnabled $false

To adjust the threshold setting at the organization level, administrators can use the command below:

Set-OrganizationConfig –AutoArchivingThresholdPercentage 96

Default Value: 96
Valid Range: 80–100

If the Organization AutoArchivingThresholdPercentage is set to 100, Auto Archiving will not take place for the entire tenant.

Aniket Gupta, Victor Legat and Exchange Online Archiving Team

Updated Oct 17, 2025

Version 5.0

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You Had Me at EHLO.

57 Comments

Satyajit321
Iron Contributor
Oct 10, 2025
First of all good initiative by Microsoft, definitely see the value in doing this. There are few areas which would further help.
* Reporting: I do understand we can use Export-MailboxDiagnosticLogs on a case by case basis. However having a clear report on when it was triggered or which users would help troubleshoot, understand more of environment, telemetry should be already available with MS
* Mailbox Usage Report: Still doesn't list the archive usage, also the export button doesn't export the quota status information. This is something long pending and for sure the data is available with Microsoft. Doesn't list shared mailboxes, resource mailboxes
Clarification Req:
* Is it applicable to unlicensed user mailboxes
* Is it applicable to EXO P2 licensed shared mailboxes, resource mailboxes
* Incase there is a mailbox that's receiving emails and increasing in an uncontrolled manner, this feature instead of blocking the growth would delay or make the situation worse by filling up the archive. Is there is a mechanism to detect, alert and prevent this from happening.
*I do get its a "failsafe mechanism" and can't be turned off for the org. But turning ELC Processing OFF should ideally stop all archiving\retention processes for that mailbox, are you saying it would still process and pick (un)flagged items based on received date
- AriasJose
  Brass Contributor
  Oct 10, 2025
  -It’s not applicable to unlicensed user mailboxes, as they don’t have the necessary Exchange Online license.
  -It is applicable to shared or resource mailboxes if they have an Exchange Online Plan 2 (EXO P2) license assigned
  - smoore6857
    Brass Contributor
    Oct 13, 2025
    Ideally Microsoft should the provide the license requirements in the future updates they have planned. For example, shared and resources mailboxes are not licensed, but they have online archive mailboxes. So, will the auto-archive feature work without Exchange licensing? If not, is EXO P1 alone sufficient or will it require EXO P1 + Exchange Online Archiving license (which technically provides the 'unlimited' archiving functionality EXO P2 provides)?
AriasJose
Brass Contributor
Oct 09, 2025
While the introduction of threshold-based Auto-Archiving in Exchange Online is technically sound and may help prevent mailbox overages, the real issue is not the change itself—but the limited time organizations are being given to prepare.
Many companies have already established well-defined archiving policies tailored to their compliance requirements, industry regulations, and internal audit frameworks. These policies are the result of years of strategic planning and governance.
Rolling out a non-optional feature with minimal lead time risks disrupting carefully managed data retention strategies. Organizations need time to assess the impact, align it with existing controls, and ensure that no compliance or operational risks are introduced.
A more collaborative rollout with extended notice and configuration flexibility would better support enterprise readiness.
- Karthik_MS
  Microsoft
  Oct 09, 2025
  AriasJose Thank you for your thoughtful and detailed feedback regarding the rollout. We want to assure you that we’ve heard this feedback clearly. Our team is actively working on an updated release plan. This includes providing controls to the admins to better control this. We will update this blog with more details in the next few days.
  - Twasielewski
    Copper Contributor
    Oct 11, 2025
    Please release soon, I really need this !!!
- Jeremy_Pratt
  Brass Contributor
  Oct 09, 2025
  Agreed that the main issue is that the time we were given was insufficient.
  
  That said, the change itself is also problematic for my org. I'm an admin in one of those orgs that have a well-defined archiving policy, and my team needs the ability to accurately predict when a given item will be moved due to the archive tag that's applied to it. If I create an archive policy tag that says an item gets moved to the archive at 5 years, I expect items that tag is applied to to move to the archive at 5 years. Not 5 years, unless the mailbox needs more space. I find it frustrating that Microsoft believes we want policies to act in a way we did not define them to.
  
  Larger orgs that have well-defined archiving policies also should have infrastructure in place to do things like monitor mailbox sizes and notify users who exceed a certain threshold. The change itself doesn't solve any problem that my org has, and it generates uncertainty about how the policies that we've defined function in production.
  
  If given more time, we could incorporate this into our existing archiving strategies. We could change our warning thresholds to be below 90%, so we could keep users under Microsoft's newly defined threshold that breaks our archiving policies if it's breached. But we'd much rather be able to disable this automatic archiving feature altogether.
  - Karthik_MS
    Microsoft
    Oct 09, 2025
    Jeremy_Pratt , Thank you for your feedback. We want to assure you that we’ve heard this feedback clearly. Our team is working on an updated release plan. This includes providing controls to the admins to better control this feature. We will update this blog with more details in the next few days.
nhawk258
Iron Contributor
Oct 09, 2025
Are we able to ensure any future updates on this item are either Roadmap or New blog posts? Adding a banner to previous posts (as was done here) does not notify people who commented on the post or have RSS feeds for blog posts.
- Nino_Bilic
  Microsoft
  Oct 09, 2025
  Yes, this is in progress.
  - Obel
    Copper Contributor
    Oct 09, 2025
    Nino_Bilic, will this also include the feature being added into the Message Center?
Flare1974
Copper Contributor
Oct 08, 2025
Our warning quota is at 92%. Now MS move the oldest items to the online archive before the warnig is triggered.
Does that mean that the warning quota never exceeds and no warning mail is send to the mailbox owner ?
would realy appreciate a configurable move quota and the option to disable this new feature.
Btw what does its means the odest items ? items of the oldest day when the folder assistent is running ?
thanks for clarification
- JoeTrombley
  Copper Contributor
  Oct 09, 2025
  90% quota limit is cutting it razor close and have seen mailboxes fill quickly. Keeping it at 92% should not trigger unless a majority of the messages are tagged as never archive. Best to lower the warning down to perhaps 75-80%
testrrr-web
Copper Contributor
Oct 08, 2025

We have quotas on our mailboxes and the useres get an infomail if the mailbox is getting full. This gives them time do delete mails they no longer need (or move them to archive). So the problem with mailflow you want to solve is not realy a problem for us. With this change its not any more possible to keep a mailbox and the archiv small. An other point is that useres who have already some folders in thier archive possibly are confused and cant find thier mail. If you copy the folder structure from the mailbox and the same strucure already existy in the archive - what is autoarchiving doing in that case (two time the same folder name)?

Please give us a possibility to disable autoarchiving!!!
VasilMichev
MVP
Oct 08, 2025
Sounds good... until it inevitably moves "those important" messages the CEO has piled in for years :D

You cannot realistically expect end users to tag items manually, especially in scenarios where the policy is not driven by their IT team and they lack proper guidance. Thus I can agree with the point some of the above commenters are making about the need for control. As well as the short notice on this.

I also want to point out that we still do not have an easy way to move messages from the Online archive back to the main mailbox. And with the clock ticking down on EWS deprecation, with no progress on Graph API support for the archive, things can get ugly.
Jeremy_Pratt
Brass Contributor
Oct 07, 2025
A global redesign of retention policies and how they work, that cannot be opted out of, with one week notice is just dumbfounding.

It took my org well over 6 months of internal negotiation to decide on our retention policies, what tags they would have, and which policy would be applied to which job codes. You're putting organizations that have carefully and thoughtfully engineered their archiving policy into an impossible position by making this kind of change. I strongly urge you to reconsider this. This is poorly thought out.
- nhawk258
  Iron Contributor
  Oct 07, 2025
  This is exactly the point I'm trying to get across. Organizations need time for change management. Dropping something like this with 8 days' notice isn't great. I did go searching, there was no mention of this on the Roadmap for Exchange either. This is the first I've heard of this feature, and it's 8 days out.
smoore6857
Brass Contributor
Oct 07, 2025
As it relates to the specific Q&A: Q: We have items/folders with the “Never Move to Archive” tag. What will happen to those items once Auto-Archiving kicks in? A: The “Never Move to Archive” tag will be still honored. That means the threshold-based Auto-Archiving will skip items/folders with “Never Move to Archive” tag.
We have our Default MRM tag set to 'Never move to archive', does this mean the auto-archiving will be skipped? If so, what is the recommended MRM policy configuration to NOT force a time-based archive policy tag so users can choose what they want, but also still allow for Auto-Archiving to work?
- Karthik_MS
  Microsoft
  Oct 07, 2025
  That is correct. When the 'Never Move to Archive' tag is applied, it is honored and are excluded from the auto-archiving process.
  - Jeremy_Pratt
    Brass Contributor
    Oct 07, 2025
    So, if we have "Default Never Move to Archive" as the tag for our non-auto-archiving retention policies, that default tag will still be honored?
    Edit: Never mind. I can see that my question is pretty much the same question and that you've already answered it.
Zohaib_Yousuf
MCT
Oct 07, 2025
I’m curious, what’s new about this rollout? It seems that auto-archiving already exists in public clouds.
Also, what happens if auto-archiving isn’t enabled for a user’s Exchange Online account? Based on my experience, the emails remain stored in the primary mailbox. However, if auto-archiving is enabled, older emails are automatically moved to the archive mailbox when the primary mailbox reaches around 90% of its storage quota.
- Karthik_MS
  Microsoft
  Oct 07, 2025
  Items from the primary mailbox are moved to the archive mailbox based on the configured archiving policy. For example, if a user’s mailbox has a “5-year move to archive” policy but reaches capacity within 2 years, it may impact the user's ability to send or receive emails.
  
  If the archive mailbox is enabled for the user, this feature will override the standard archiving policy and begin archiving items proactively once the mailbox reaches a critical threshold. This helps prevent any disruption to mail flow.
  
  However, if the archive mailbox is not enabled, the system will not provision one automatically, and the current configuration will remain unchanged.
nhawk258
Iron Contributor
Oct 07, 2025
So we get 8 days' notice for a feature that cannot be disabled? I understand the principle behind this, but there really should be the ability to disable this feature without having to also disable a user's archive.
- Nino_Bilic
  Microsoft
  Oct 07, 2025
  Can you help me understand this a bit more:
  
  In which scenario would you want to disable this (with understanding that the alternative of time-based archiving is that the user runs out of mailbox quota and has disruption of service)?
  - MailMan7
    Copper Contributor
    Oct 08, 2025
    I would like to see a mailbox attribute where admins can set this feature to give admins more control. Example :
    Set-Mailbox "John Doe - JD" -AutoArchiveEnabled $False/$True
    Then we as IT Dept could set VIP's to disabled for this feature and handle the Mailbox Quota exceeded process differently.