Fixing Outlook 2013 “Outlook is unable to connect to the proxy server” errors on Windows 10


Out of nowhere, I started to get some weird proxy server errors from Outlook 2013 to our Exchange on-prem servers. We knew the SSL certs were fine, it was just me getting the error and I’m running Windows 10 Insider Builds, so I figured it was just something stupid that changed. 

“There is a problem with your proxy server’s security certificate.
Outlook is unable to connect to the proxy server … (Error Code 800000000).” 

This made no sense. I’m sure it could be something got garbled with recent updates on Insider between older Office versions or something. I also check settings around any add-ons, etc. but nothing. I deleted everything in AppData around Outlook and still nothing worked. 

In the old pre-Windows 10 days, I would immediately have just deleted the Mail Profile and created a new one, but that isn’t easy to get to right away anymore even though it is still around in Windows for legacy purposes. It finally came to that after trying everything else. 

Here is what I did to resolve it. 

  1. Right-Click the Windows Start Menu in Windows 10, and Run “Control Panel” This is the old Windows Control Panel still hiding inside Windows 10.
  2. In the legacy Windows Control Panel, you can open “Mail (32-bit)” and get direct access to what is going on with the Outlook/Windows Mail Profile.3.
  3. Delete the Show Profile(s) there. 
  4. Then remove the profiles affected
  5. Logout of Windows 10. 
  6. Log back in, Start Outlook 2013 and setup the profile again. 

This resolved the issue. 

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