You may receive the error message There is a problem with the proxy server’s security certificate when Outlook tries to connect to a server using an RPC connection or an HTTPS connection. In this article, we will identify the potential causes and suggest the most adequate solutions to resolve this problem.
When you experience this problem, you will receive the following complete error message;
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 webmail.domain.com.
Outlook is unable to connect to the proxy server. (Error code 0)
Possible variations of the error message with the associated error code when the error occurs can be one of the following;
- There is a problem with the proxy server’s security certificate,% s. Outlook cannot connect to this server.
- There is a problem with the proxy server’s security certificate,% s. The name on the security certificate is invalid or does not match the name of the site. Outlook cannot connect to this server.
- There is a problem with the proxy server’s security certificate,% s. The security certificate is not from a trusted certification authority. Outlook cannot connect to this server.
According to Microsoft documentation, this problem can occur if one or more of the following conditions are true:
- Connection to the server requires a certification authority (CA).
- You did not trust the root CA.
- The certificate may be invalid or revoked.
- The certificate does not match the name of the site.
- A third-party add-on or a third-party browser add-on is preventing access.
There is a problem with the proxy server’s security certificate – Outlook error
If you are facing this issue on your Windows 11/10 PC, you can try our recommended solutions below in no particular order and see if it helps to fix Outlook error message. There is a problem with the proxy server’s security certificate.
- Check the proxy server certificate
- Install the trusted root certificate
- Disable third-party add-on in Outlook
- Disable third-party browser add-ins
- Manually configure Exchange proxy settings in Outlook
Let’s take a look at the description of the process involved regarding each of the solutions listed.
1]Check the proxy server certificate
This solution requires you to verify the certificate and then contact your system administrator to resolve this issue. There is a problem with the proxy server’s security certificate problem.
To verify the proxy server certificate, follow these steps:
- Open Edge browser on your Windows 11/10 PC.
- Type or copy and paste the URL below into the web browser’s address bar and press Enter. Replace the Server name placeholder with the name of the RPC server or the name of the secure server.
- Then click on the padlock icon in the address bar.
- In the flyout menu, click Connection is secure.
- Click on the Security certificate to view the security certificate.
- In the property sheet of the security certificate, click the button Details tongue.
- Now write down the information in the fields highlighted in the image above.
The Valid for must indicate the date until which the certificate is valid. The data in the Topic must match the site name – and if not, contact your IT administrator.
2]Install the trusted root certificate
This solution requires that you install the trusted root certificate on the Windows 11/10 client computer.
Proceed as follows:
- When the error occurs and you are prompted with the Certificate dialog box, click Install the certificate.
- Click on Next.
- Click to select the Place all certificates in the following store check box.
- Click on Browse.
- Click on Trusted Root Certification Authorities.
- Click on Okay.
- Click on Next.
- Click on To finish.
- Click on Okay.
3]Disable third-party add-on in Outlook
Another viable solution to fix the error in sight is to disable the third-party add-in in Outlook. To do this, you must first start Outlook in Safe Mode, and if Outlook successfully opens in Safe Mode, the error is likely to be triggered by third-party add-ons.
To disable third-party COM add-ins in Outlook, follow these steps:
- Start Outlook in Safe Mode.
- On the To file menu, click Options > Complements.
- In the Manage box click COM add-ins > Go.
- Now uncheck the box of any third party add-ins you want to disable.
- Restart Outlook.
4]Disable third-party browser add-ins
Depending on your browser, this solution requires you to disable third-party browser add-ins and see if that helps resolve the issue. Otherwise, try the next solution.
5]Manually configure Exchange proxy settings in Outlook
To manually configure Exchange proxy settings in Outlook, follow these steps:
- Open Microsoft Outlook.
- Move towards Account settings > More settings > Link > Exchange proxy settings.
- Now type the address below into the Connect only to proxy servers that have this principal name in their certificate field.
Otherwise, to achieve the same result, follow these steps:
- hurry Windows key + X to open the Advanced User menu.
- Faucet A on the keyboard to launch PowerShell in administrator / elevated mode.
- In the PowerShell console, type or copy and paste the command below and press Enter.
Set-OutlookProvider EXPR -CertPrincipalName:$null
- Quit PowerShell when the cmdlet runs.
Similar article: Error 0x80004005, Operation failed in Outlook
Why is my Outlook unreliable?
If you have met the Outlook.com security certificate error or the error message The server you are connected to uses a security certificate that cannot be verified – the most common reason behind this error is that you have the wrong hostname configured in Microsoft Outlook.
Why am I getting a security certificate warning?
The reason you might get a security certificate warning on your Windows 11/10 PC is due to the incorrect date and time. Security certificates are used by web browsers and computers to make sure that a particular site is safe. So if your computer has an incorrect date and time, the certificates may appear invalid and your web browser will start issuing security warnings. So make sure the date and time are correct on your computer.
How can I get rid of security certificate errors?
To eliminate security certificate errors in Windows 11/10, you must disable this option. Follow these instructions:
- Open the Control Panel.
- To select internet options.
- Click it Advanced tongue.
- Scroll to Security section.
- In the Security section, uncheck the Warn on certificate address mismatch option.
- Click on To apply > Okay to save the changes.
- Restart your PC.
Why is my email certificate unreliable?
The most likely reason that your email certificate is unreliable is due to incorrect email settings. When you receive an insecure certificate error message for your email, it is because you have synchronized an email account that belongs to you or that belongs to your organization’s domain, but there is an inconsistency in the SMTP / IMAP settings, port settings or domain name settings.