There is a problem with the proxy server’s security certificate. The name on the security certificate is invalid or does not match the name of the target site outlook.office365.com. Outlook is unable to connect to the proxy server (Error Code 0)

There are many possible causes for the Outlook Error 0 message.
I’ve spent some time trying to figure out what’s causing this and also most of the solutions found on Internet didn’t help as they were suggesting server-side operations.
As I knew there’s nothing wrong with our Exchange server settings I focused only on the client-side to find what’s causing the error.
After trying all kind of workarounds it proved to be just a tickbox that needed to be unticked: the one from Internet Explorer – LAN – Connections – Use a proxy server for your LAN …
Probably some virus/malware ticked the ‘Use a proxy server’ box…

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4 Responses to There is a problem with the proxy server’s security certificate. The name on the security certificate is invalid or does not match the name of the target site outlook.office365.com. Outlook is unable to connect to the proxy server (Error Code 0)

  1. bill says:

    SOLVED – can’t thank you enough. Been trying to fix this for hours and this simply change got me connected. Just opened IE, tools, Internet connections, LAN settings. What this has to do with Outlook, I have no idea, but it worked. Thanks so much!

  2. James says:

    Excellent advise. Like Bill I have used other recommendations, but I looked for the most recent recommendation and it fixed the issue right away. Cannot thank you enough!

  3. Krishna says:

    Superb!! I have been trying to fix these for the past few days and finally this simple change in settings worked. Thanks a lot!!

  4. shamsheer Shaik says:

    Resolved. Thanks

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