Can’t access Office 365 in Outlook: “The name on the security certificate is invalid or does not match the name of the target site”

Ran into this one recently.  When accessing Office 365 via Exchange from Outlook 2013, an error pops up.

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 is unable to connect to the proxy server. (Error Code 0)

When using auto-configuration to set up the Exchange connection to Office 365 in Outlook, these proxy settings are automatically entered.


The URL is “” which appears to be what the error message is talking about.  For some reason, it is unable to connect or it connects to the wrong server and the SSL certificate looks bad.

It took a while to pin down the solution, but AkikoS in this thread figured it out.  Visit the “Internet options” control panel and make sure that the option to use a proxy server for the LAN is unchecked.  (This appears in the “Connections” tab under the “LAN settings” button.)


Once the box is cleared, if you start Outlook again the problem should be resolved.  In my case, something appears to be re-checking this box when the machine boots and that’s going to take a little more digging to figure out.

Update, October 25, 2014:

Problem started getting worse (proxy settings checkbox checked every few minutes).  I used Process Monitor to track it down.  It was a piece of adware that was trying to be tricky.  Process Monitor indicated that a few different QuickBooks processes and an Akamai process were hosting a local proxy and setting the proxy checkbox.  I ended up tracking it down to a service called “RocketTab” which had installed itself in C:\Program Files (x86)\Search Extensions.  After uninstalling it, the problem went away.

50 thoughts on “Can’t access Office 365 in Outlook: “The name on the security certificate is invalid or does not match the name of the target site””

  1. Thank you, this worked after I removed all of the information in the Advanced section. Weird….

  2. Hello Aaron, thank you for this tip.

    I too am having the issue of the check box being rechecked each time I close out IE. Have you been able to discover a fix to this?

    Thanks in advance.

  3. If you find that you have that proxy server box checked, but don’t know what a proxy server is or had no intentions of using one, make sure to scan your machine for malware. That’s a common sign of an infection of some sort since it can be used to intercept your Internet traffic. Some good free scanners are MalwareBytes AntiMalware and Spybot Search and Destory.

    If this on a business computer it’s possible that they activated the proxy setting, but in that case they should also have it locked so you can’t edit it.

  4. What a mess! You saved one frustrating week! Thanks for your work and then for publishing the solution. Thank you to AkikoS as well. This worked great.

  5. Hi, Great! none of the MS guys posts or solution has this. it worked out great for me. I was struggling for couple of hours reading different posts and this really helped and worked! thank you.

  6. This works until the machine restarts. I cleared out the Advanced info under the proxy server info and ran a malware scan and quarantined what was discovered. The check mark comes back everytime the machine restarts. Any other suggestions??

  7. Great post! I ran into the same issues of the box re-checking itself. After further looking into this i found spyware located under:


    After deleting/removing the spyware i was able to uncheck the box without it re-checking itself.

    Hope this helps!

  8. Thanks for this – spent far too long trying to resolve the issue before I came across this and then it was so simple!

  9. Run hitman pro (32 or 64 bit). It will tell you if there is a proxy and it will fix it. Very quick and easy fix.

  10. Thank you for this brief, yet working fix. Printing your directions out, I was able to fix this for a coworker in less than a minute. Excellent work!

  11. I tried the same procedure it worked and when i restart the machine and try accessing outlook it troughs the same error message.

  12. If you find the box keeps getting checked to “Use a proxy server for your LAN” after unchecking it, try checking the box for “Automatically detect settings”. This worked for us. We would uncheck the “Use a proxy box” but as soon as we tried to open an email in Outlook it would go back to “Trying to connect” and the box would have a check on it again. After checking “Automatically detect settings” it seems to be working fine now.

  13. Thanks for much for your post. I had to make these setting both in IE and Chrome to get it working. But now after two weeks I can finally use my Outlook again.

  14. Dude….. you are awesome. Am in a 24/7 support and my laptop got this issue. I was breaking my mind for the last 4 days and am working from home due to some personal reasons.. you saved my job man…..

  15. I had the same problem, when i restarted the machine the checkbox got back. Then i found out that i had RocketLab installed. Uninstalled RocketLab and now it works great!!

  16. Thanks for the info! It worked like a charm. Now to find out how and why this setting was changed on me.

  17. Thank you!!! Your tips worked quickly to fix Outlook. I also somehow had RocketLab, which I promptly deleted!!!

    Thanks again.

  18. Thank you for your help
    This worked for me.
    Exactly the problem was because of the Rocket tab and Proxy settings.

  19. Brilliant – thanks for posting – solver my problem.
    A couple of bullets to the heads of the RocketTab devs wouldn’t go astray.

  20. I too faced the same problem regarding “Rocket Tab” and after uninstalling that Tool I found Outlook Effectively working.

    Thank You For the Tip.

    Yours Faithfully,
    Sk Thanveer Ahamed.

  21. Thanks so much brooooo…
    thanks for posting – solver my problem.

    “Rocket Tab” it’s all problem

  22. very very nice article, thanks for the sharing with us.Toll-Free UK 0800-098-8858 for set-up wireless router, broadband router set-up, router Wi-Fi problems, how to re-setup your modem.

    netgear router customer support
    netgear router phone number

Leave a Reply

Your email address will not be published. Required fields are marked *