Microsoft announced on Monday that it will soon block mobile devices running outdated email software from accessing Exchange Online services until they're updated.

As the Exchange Team explained, devices running Exchange ActiveSync versions below 16.1 will no longer be able to connect to Microsoft's cloud email service after March 1, 2026.

Exchange ActiveSync (EAS) is a Microsoft Exchange protocol to synchronize email, calendar, contacts, and tasks on mobile devices, and it is enabled by default for new user mailboxes.

The change affects only devices using native email apps and Exchange Online, and does not affect on-premises Exchange Server installations. Microsoft added that devices using Outlook Mobile to connect to Exchange Online are not affected, since this app does not rely on the EAS protocol.

"We want to inform our users and organizations about an important upcoming change regarding Exchange ActiveSync (EAS) device connectivity to Exchange Online," the Exchange Team said.

"Starting March 1, 2026, devices running ActiveSync versions lower than 16.1 will no longer be able to connect to our services. EAS 16.1 was released as a part of Exchange Server and Exchange Online in June 2016."

Popular native email applications for smartphones will also require updates to continue functioning. For instance, Google and Samsung are currently updating their email applications to support the newer protocol version.

However, Apple's iOS Mail app already supports ActiveSync 16.1 since iOS 10, so iPhones running iOS 10 or later are compatible and shouldn't experience any issues accessing Exchange Online.

Microsoft provided IT administrators with the following PowerShell command to generate a report of all devices using older EAS versions within their organizations before the March 2026 rollout:

Get-MobileDevice | Where-Object {($_.ClientType -eq 'EAS' -or $_.ClientType -match 'ActiveSync') -and $_.ClientVersion -and ([version]$_.ClientVersion -lt [version]'16.1')} | Sort-Object UserDisplayName | Select-Object UserDisplayName, UserPrincipalName, DeviceId, DeviceModel

"This decision comes after extensive collaboration with multiple licensed device and application vendors to ensure a smooth transition for as many users as possible," the Exchange Team added.

"If users and organizations keep their devices and applications updated to the latest supported versions, there should be minimal disruption in service. We encourage everyone to verify their devices and applications are up to date before the change takes effect."

Last month, Microsoft fixed an issue that prevented some Microsoft 365 users from connecting to email servers via Exchange ActiveSync with Outlook desktop clients.