Microsoft has shared a fix for Outlook connection errors that iOS and Android users may experience with mailboxes in certain Exchange environments.

Affected users will see the error messages “ has been blocked on this device by your administrator”.

“The error occurs in a hybrid Exchange environment, for mailboxes in on-premises Microsoft Exchange Server or Exchange Online,” the company said. said in a supporting document released on Tuesday.

According to Redmond, the likely cause is a missing Exchange ActiveSync (EAS) access rule that would allow users using the Outlook iOS and Android apps to connect to the Exchange Online server.

To resolve these connectivity issues, administrators should ensure Hybrid Modern Authentication is enabled and add a new Exchange Online access rule for Outlook mobile apps.

The procedure required for this requires them to:

• Verify that you have enabled support for Hybrid Modern Authentication in your organization (more information is available in this supporting document)
• Create an EAS device access rule in Exchange Online that allows connections from Outlook for iOS and Android. To do this, run the following commands:
  • Connect-ExchangeOnline
  • New-ActiveSyncDeviceAccessRule -Characteristic DeviceModel -QueryString "Outlook for iOS and Android" -AccessLevel Allow

Last year, Microsoft also provided a workaround for a separate and ongoing known issue causing connection issues for certain Outlook for Microsoft 365 customers and prevent them from accessing their accounts.

This issue only affects users who sign in to Outlook using their Outlook.com accounts or those who have already added the accounts to their Outlook profiles.

Until a fix is ​​available, Redmond recommends disabling support diagnostics, which would resolve the root cause of these connection issues.

“As a workaround, you can disable Support Diagnostics, which disables the option to submit an In-App ticket using Help and then selecting Contact Support,” Microsoft said in October. .

“The bug is related to how Outlook authenticates for diagnostics in certain situations.”

The company also rolled out a fix for another known issue since August that was causing Outlook for Microsoft 365 freezes and crashes after launch.