Deadline March 1, 2026: What administrators need to know about Exchange ActiveSync (EAS) now.
Microsoft continues to clean up the legacy protocols. A recent announcement confirmed that from March 1, 2026 , Exchange Online will no longer allow connections from email clients that use outdated versions of the Exchange ActiveSync (EAS) protocol.
For companies, this means that it is time to check mobile access in order to avoid connection interruptions in the coming year.
What exactly is changing?
From the deadline, Microsoft will block all EAS connections that have a version number less than 16.1 .
- The background: Version 16.1 was already introduced in 2016. Microsoft is focusing on this supported version for security and stability reasons.
- The consequence: Mobile devices or mail apps that still transmit on older standards will no longer be able to send or receive emails and synchronize calendars from March 2026.
Who is affected?
The good news first: Most modern smartphones are secure.
- Apple iOS: Has been using EAS 16.1 since iOS 10.
- Android (Samsung/Google): According to Microsoft, the standard mail apps of the major manufacturers are currently being updated to 16.1.
It becomes problematic with:
- Very old mobile devices that haven’t been updated in years.
- Certain third-party mail apps that do not implement the protocol properly.
- “Dead bodies” in the Exchange: Old device partnerships that were never deleted.
Recommendation for action for IT admins
Nobody likes surprises on Monday mornings. We therefore recommend running a scan of your tenant early on to identify outdated clients.
This can be done efficiently via PowerShell. You can use the following command to check which devices are still running old protocols:
Get-MobileDevice -ResultSize Unlimited | Where-Object {($_.ClientType -eq 'EAS' -or $_.ClientType -match 'ActiveSync') -and $_.ClientVersion -and ([version]$_.ClientVersion -lt [version]'16.1')} | Select-Object UserDisplayName, DeviceModel, ClientVersion, Identity | Format-TableRecommendation: Switching to the Outlook Mobile App
This end-of-life date is the perfect occasion to fundamentally rethink your mobile device strategy. The ActiveSync protocol is robust, but technologically outdated. It does not offer the safety and comfort features that modern work requires.
Why I (and Microsoft) recommend the Outlook mobile app:
- Security: Outlook Mobile supports modern authentication (MFA) and app protection policies via Microsoft Intune much better than native mail apps via EAS.
- Features: Functions such as the “Relevant Inbox”, integrated Teams meetings or the direct editing of Office documents are missing from classic EAS connections.
- Future-proofing: Outlook Mobile does not use the old EAS protocol and is not affected by the shutdown of versions below 16.1.
Conclusion & Support
The end of old versions of ActiveSync is a logical step towards a more secure cloud environment. There is still time until March 2026, but as is so often the case in IT, preparation is everything.
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