How To Fix ‘Outlook Certificate Error Office 365’?


While using Outlook on Office 365, you may come across many errors, but when it comes to the most common error, then it has to be Outlook Certificate Error Office 365. The error occurs when an admin uses self-published certificates.

When it comes to fixing this error, then you will find it very hard. Even understanding this error is difficult, as the error defines the security certificate of your email server, which has expired due to several reasons. If you are dealing with such an error, then you need to install an updated certificate.

  • While experiencing this error, you will see an error message popping up on the screen asking you to grant permission.
  • You won’t be able to hide the pop-up or turn off the option no matter what you do. This error message also means that the server isn’t matching the name with the account settings that you are using.
  • The error can also arise when the web browser’s settings are configured in the wrong way.

To fix the problem, you can follow the process explained in the following section:

Apparent fixes to fix Outlook Certificate Error:

You need to know the problem to be able to fix it on your own. Find out how to fix the problem in the next section:

Inspect the Certificates

To fix the Outlook Certificate error, you need to check all the certificates. To do so, you need to contact the system admin followed by getting the admin rights of the device.

Once you do that, you will have to get the connection to any server that your feel is safe and secure. Or, you can connect to the RPC server within the Internet Explorer. Then, click the ‘Enter’ button on your keyboard.

You will have to navigate to the Padlock symbol. This icon is going to be present on the lower right corner of the web browser window. Double-tap on the icon to select it.

After that, you need to go to the new window followed by clicking on the ‘Details’ tab. Then, acquire the information from the respective fields that you want to display of your device. However, keep in mind that the information present in the field needs to be the same as that on the website.

At last, you need to restart Outlook. If you are prompted to log in with the right login details, then do the same. Now, your error will most likely be fixed.

Get your Email Server’s Address

You need to navigate to the ‘Start’ menu followed by clicking on the dialog box. Then, enter ‘cmd’ in the box followed by launching the Command Prompt.

After that, you need to type ‘ping’ to get the IP address along with the server name of the host.

If you find that, the server name in the ping results is exactly what’s given on the certificate, then you will have to use it as the mail server name in your MS Outlook account.

In case, there is another name, then you need to use it as the server name in the MS Outlook app.

Build a New DNS Record

In case, the previous two methods don’t fix the problem of Outlook Certificate error Office 365, then you will have to make a new DNS record followed by checking if the issue gets resolved or not.

To do so, you need to use the certificate that is on the certificate itself. Reverse proxies and CAS servers use this name. You will have to use the same name for both external DNS, as it is available in the certificate.

For fixing the internal IP of the CAS server, you must have the internal DNS. For removing the public IP of the CAS servers, you need the external DNS.

In case, you are using the reverse proxy, then you should configure the external IP to change the public IP of the reverse proxy.

That is how you can fix the problem of Outlook certificate error Office 365. In case, the problem continues to exist, then you can get in touch with Outlook experts.


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