Good news email hoarders - Microsoft Outlook will start auto-archiving your oldest messages to protect your inbox

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Outlook adds new auto-archiving feature

The Microsoft Outlook logo on a laptop screen
(Image credit: Shutterstock / monticello)
  • New Outlook auto-archiving springs into action when your mailbox hits 90% capacity
  • Existing archiving and data retention policies remain unaffected
  • Auto-expanding archives are also on the horizon

Microsoft will soon start rolling out new threshold-based auto-archiving for Exchange Online in a bid to prevent ‘mailbox full’ errors.

The feature will work by automatically archiving the oldest items when storage capacity reaches capacity, marking a change from time-based archiving (like ‘move after two years’) as email volume and attachment size continue to grow.

Public cloud customers will see the change in October 2025, with government clouds getting the update in November.

Outlook will start automatically archiving old emails

The Exchange Team explained in a blog post that the oldest emails would become automatically archived once mailbox quota approaches 90%. This comes from feedback that users wanted “proactive and automated space management” solutions.

Microsoft stressed that auto archiving does not replace or interfere with companies’ existing archiving policies – instead, it acts as a failsafe when space gets tight. The ‘Never Move to Archive’ tag will also be honored, keeping those emails in the main inbox.

Auto archiving won’t interfere with data deletion and retention policies either, because emails will still be stored within the archive.

However, users will not be able to disable auto-archiving. “It is a failsafe mechanism to prevent any mail flow disruptions and only gets triggered when mailbox utilization crosses 90% (Critical) threshold,” the company explained.

A separate Microsoft roadmap entry, tracked as 395793, details efforts to support auto-expanding archives beyond the normal 100GB quota limit. Rollout is imminent, according to the note.

An October 8 update to the blog post notes that a revised release plan for auto-archiving will be communicated “in the near future” as a result of customer feedback. As of the time of writing, the October 7 blog post has not been updated.

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Craig Hale
Craig Hale

With several years’ experience freelancing in tech and automotive circles, Craig’s specific interests lie in technology that is designed to better our lives, including AI and ML, productivity aids, and smart fitness. He is also passionate about cars and the decarbonisation of personal transportation. As an avid bargain-hunter, you can be sure that any deal Craig finds is top value!

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