Microsoft has announced a significant security update targeting Exchange Online connectivity.
Starting March 1, 2026, mobile devices running Exchange ActiveSync (EAS) versions older than 16.1 will no longer be able to access Exchange Online mailboxes.
The phased approach marks nearly a decade since the release of EAS version 16.1 in June 2016.
Microsoft states this decision follows extensive collaboration with device and application vendors to minimize service disruptions and enhance the overall security posture of Exchange Online environments.
The policy specifically targets mobile devices using native email applications that rely on the EAS protocol.
Users running outdated client versions must update their devices or applications before the March deadline to maintain continuous email access.
Microsoft emphasizes that users keeping their devices and applications current should experience no service interruption.
The restriction applies exclusively to Exchange Online users and does not affect on-premises Exchange Server environments.
Affected Applications and Devices
The iOS Mail App remains compatible with devices running iOS 10 or later, as these systems adopted EAS 16.1 by default.
Gmail and Samsung Mail are currently undergoing version updates; users need only keep their apps up to date to switch to the required version before the deadline automatically.
IT administrators should proactively identify outdated devices in their organization using Microsoft PowerShell commands.
Get-MobileDevice -ResultSize Unlimited | Where-Object {($_.ClientType -eq 'EAS' -or $_.ClientType -match 'ActiveSync') -and $_.ClientVersion -and ([version]$_.ClientVersion -lt [version]'16.1')} | Sort-Object UserDisplayName | Select-Object UserDisplayName, Identity, DeviceId, DeviceModel | Format-ListThis tool generates comprehensive reports of all devices and applications currently using ActiveSync versions below 16.1, enabling precise identification of affected users.
Organizations are strongly advised to notify affected users well before the March 2026 cutoff. Users should update their device firmware or email applications to ensure uninterrupted access to their mailboxes.
Microsoft’s move prioritizes security modernization while providing adequate transition time for enterprise environments.
This represents the company’s broader commitment to maintaining a secure and reliable Exchange Online infrastructure through continuous protocol improvements and vendor collaboration.
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