Outlook Desktop Exchange ActiveSync connections stopped working in Version 2401

Last Updated: February 29, 2024

ISSUE

After updating to Version 2401 Build 17231.20182 Outlook stops connecting when using the Exchange ActiveSync (EAS) protocol.

STATUS: FIXED

This issue is fixed in Outlook Desktop Version 2402 Build 17328.20068 and higher. To install the update right away select File > Office Account > Update Options > Update Now.

If you worked around the issue by reverting to the prior build, re-enable updates by selecting File > Office Account > Update Options > Enable Updates.

Workaround:

Revert the Office M365 Click-to-Run installation to Version 2312 Build 17126.20132. 

To do this:

1. Exit all Office applications.

2. Select Start, type cmd in the Search box, right-click Command Prompt (or cmd.exe), and then select Run as administrator.

3. In the command prompt dialog window, type the following two command lines, pressing Enter after each command line:
   
   cd %programfiles%\Common Files\Microsoft Shared\ClickToRun
   officec2rclient.exe /update user updatetoversion=16.0.17126.20132

4. When the repair is done, open Outlook and select File > Office Account.

5. Select Update Options and choose Disable Updates.

6. Add an appointment on your calendar for a future date April 1, 2024, to check back to this topic to confirm the issue is fixed. If it is, re-enable updates by selecting File > Office Account > Update Options > Enable Updates.

Additional Resources

Change the Microsoft 365 Apps update channel for devices in your organization

How to revert to an earlier version of Office