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How to Fix Outlook Error 0x80040115: Connection to Microsoft Exchange Failed (2026)

Are you unable to send or receive emails due to Outlook error 0x80040115? This "Cannot connect to server" glitch has spiked following the January 2026 Windows security updates. Whether you are using Outlook 365 or Classic, this error is currently paralyzing business communications across the US and UK. Here is the 2-minute fix to restore your connection right now.

​Why is Outlook Error 0x80040115 Happening Today?

​The 0x80040115 error typically occurs when the Outlook client fails to sync with the Microsoft Exchange server. In January 2026, the root cause has been identified as a DNS cache conflict and a profile encryption bug triggered by the KB5074109 update. If your status bar says "Disconnected" or "Trying to connect," the server is rejecting your local security token.

​4 Quick Steps to Fix Outlook Connection Errors

​Follow these verified methods to get back online:

  1. ​Flush Your DNS Cache: This is the most successful fix today. Open Command Prompt as Administrator and type: ipconfig /flushdns. Hit Enter and restart Outlook. This clears the outdated server routes caused by the update.
  2. ​Enable Encryption Settings: * Go to Control Panel > Mail > Show Profiles.
    • ​Select your profile and click Properties > Email Accounts.
    • ​Select your Exchange account and click Change > More Settings > Security.
    • ​Check the box: "Encrypt data between Microsoft Outlook and Microsoft Exchange". Click OK and restart.
  3. ​Launch in Safe Mode: Press Win + R, type outlook.exe /safe, and hit Enter. If it works, a faulty third-party add-in is blocking your connection. Disable your add-ins one by one.
  4. ​Repair the OST File: Use the ScanPST.exe tool (found in your Office installation folder) to repair your local data file. If your file is stored on OneDrive, move it to a local folder to avoid the January 2026 sync bug.

​Official Microsoft Status

​Microsoft is currently investigating reports of Outlook "hanging" and failing to exit properly after the recent patches. Until a permanent fix is released in February, flushing the DNS and enabling data encryption are the only ways to bypass the 0x80040115 block.