Entitlement.Diagnostics.office.com Certificate Error: 5 Ways to Fix It

Did you experience the entitlement.diagnostics.office.com certificate error while opening Outlook in Office 365? The error may be so persistent that the Outlook security alert certificate keeps popping up. There could be various reasons for this issue.

This article will explore what the issue is and dependable solutions to try. We will explore five solutions so that you can have a variety to select from. However, we cannot talk about workable solutions without knowing the problems. So let’s talk about why the error occurs in the first place.

Why do I get certificate errors in Microsoft 365?

The error may chiefly occur due to any of the following reasons:

• Unchanged old domain name: The old domain name must correspond with the new Outlook setup.
•  Invalid Certificate Name: It is also possible that the name on the security certificate is invalid or does not match the site name.
•  Expired Certificate: The website or service you are trying to access may have an expired SSL certificate. This issue will cause certificate errors in Microsoft 365.
•  Self-Signed Certificate: If the website or service you are trying to access uses a self-signed SSL certificate, they may provide a certificate that Microsoft 365 does not recognize.
•  Incomplete Certificate Chain: If a website uses an SSL certificate from a Certificate Authority, there might be an issue with the certificate chain if one of the intermediate certificates is missing.
•  Mixed Content: If a website you are trying to access uses HTTPS but some of the resources it is accessing uses HTTP, it can cause mixed content issues that will trigger certificate errors in Microsoft 365.
•  Wrong Hostname: Another issue that can cause a certificate error is if the SSL certificate on the website or service you are accessing is not generated for the correct domain name.

We have written several guides on how to resolve other errors. You can also check them out.

How do I fix the entitlement.diagnostics.office.com certificate error?

1. Verify the certificate name

1. Choose the View Certificate option on the Security Alert showing the Outlook security certificate error.
   
2. Then, tap the Issued to Name option and see if the name on the certificate an on the mail server matches.
   
3. If the names on the certificated do not match, alter the names to match, then restart Outlook.
4. But if the certificate has different names, try each hostname. Remove the correct mail server from your Internet Service Provider if none is correct.
5. Once you verify the certificate name successfully, the entitlement.diagnostics.office.com certificate error pop-up should stop.

2. Change the outgoing SMTP port

1. Launch the Outlook app and click the File tab.
2. Then, select the Info tab and click the Account Settings option.
   
3. When the Account Settings window opens, choose your email account under the E-mail tab and tap Change.
   
4. After that, click More Settings and choose the Advanced tab.
5. Finally, change the Outgoing server (SMTP) port and tap OK to save the changes.
   

3. Run System File Checker scan

1. Press the Windows and S keys together and enter cmd in the search field.
2. Then, select Run as administrator on the right side to launch the Command Prompt as an admin.
   
3. When UAC prompts you, click on Yes to proceed.
   
4. After Command Prompt opens, enter the following command into the console and hit Enter to begin an SFC scan:
   sfc /scannow
   
5. When the scan is complete, enter the command below and press Enter to run the command:
   DISM.exe /Online /Cleanup-image /Restorehealth
   
6. Finally, it would be best to restart your computer to implement repairs.

4. Launch Outlook in Safe Mode and Disable Add-ins

1. Press the Windows + R keys simultaneously to launch the Run dialog. Type Outlook /safe in the text field, then press the Enter key.
   
2. When the Choose Profile window opens, click the OK button. If you receive a password prompt, enter it, and click Accept.
   
3. Once that is done, open Outlook, locate the File, and click the Options.
   
4. In the Outlook Options window, click on the Add-ins.
5. Under View and manage Office Add-ins, select COM Add-ins in the Manage window.
6. Then, tap the Go button.
   
7. When the COM Add-ins window opens, recall every add-ins enabled under the Add-ins available section.
   
8. Then, uncheck all the checkboxes to disable the Add-ins.
9. Finally, tap on the OK button and close Outlook.

5. Run the reset command

1. Press the Windows + R key to open the Run dialog, enter outlook.exe /resetnavpane, then tap the Enter key or click on the OK button.
   
2. After that, the command will remove all the customization related to the navigation pane and attempts to fix Outlook.

In conclusion, the four steps outlined above can troubleshoot, identify, and fix entitlement.diagnostics.office.com certificate errors quickly and easily, ensuring that you no longer have to worry about access problems.

By understanding the underlying cause of certificate errors and the different ways to rectify these errors, you can ensure that you can access HTTPS websites without any further delays.