problem with the proxy server’s security certificate – Outlook error, you may get an error message that says “There is a problem with the proxy server’s security certificate.” Here’s what’s causing the problem and how to fix it. When you try to connect to a server by using RPC or HTTPS, you may receive an error message that says “There is a problem with the proxy server’s security certificate.” In this post, we’ll identify the potential causes of this error and offer some solutions to fix it.
The following full error message is displayed when this issue occurs, When you encounter this issue, you’ll receive the following full error message.
Possible error messages with accompanying error codes when the error occurs can include any of the following:
- The proxy server’s security certificate has a problem, %s. Outlook can’t connect to this server.
The security certificate for the proxy server %s has invalid or mismatched name. Outlook can’t connect to the server.
- The security certificate for the proxy server is not from a trusted authority, so Outlook can’t connect to the server.
This issue may occur if one or more of the following conditions are true, according to Microsoft documentation.
- The server connection requires a certification authority (CA).
- You haven’t trusted the certification authority at the root.
- The certificate may be invalid? The certificate may be invalid or revoked.
- The certificate doesn’t match the site’s name.
- A third-party plugin or browser extension is preventing access.
There is a problem with the proxy server’s security certificate – Outlook error
If you’re having trouble with the proxy server’s security certificate on your Windows 11/10 PC, there are some solutions you can try below.
- Check 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 look at how each of these solutions works.
1] Check Proxy server certificate
There is an issue with the security certificate of the proxy server. You will need to check the certificate and then contact your system administrator to resolve this.
To check the proxy server certificate, do the following:
- Open Edge on your Windows 11/10 PC.
- Replace the server_name placeholder with the RPC server name or the secure server name.
- Next, click on the padlock icon in the address bar.
- Click “Connection is secure” on the flyout.
- To view the security certificate, click on the security certificate icon.
- Click on the Details tab of the Security Certificate properties sheet.
- In the image above, make a note of the information in the fields highlighted.
The “Valid to” field should show the date when the certificate expires. If the data in the “Subject” field does not match the site name, contact your IT administrator.
2] Install the Trusted Root Certificate
You will need to install the Trusted Root Certificate on the Windows 11/10 client computer in order to use this solution.
Do the following:
- When you’re prompted with the Certificate dialog box, click Install Certificate.
- Click Next.
- Select the “Place all certificates in the following store” check box.
- Click Browse.
- Click Trusted Root Certification Authorities.
- Click OK.
- Click Next.
- Click Finish.
- Click OK.
3] Disable third-party add-on in Outlook
Another possible solution to the error in view is to disable third-party add-ins in Outlook. To do this, you first need to start Outlook in Safe Mode. If Outlook opens successfully in Safe Mode, then it is likely that the error is caused by third-party add-ins.
To disable third-party COM add-ins in Outlook, follow these steps:
- Start Outlook in Safe Mode to prevent crashes and data loss.
- On the File menu, click Options > Add-Ins.
- In the Manage box, click COM Add-ins, and then click Go.
- Now, disable the checkbox for the third-party add-ins that you want to disable.
- Restart Outlook.
4] Disable third-party browser add-ins
Depending on your browser, you may need to disable third-party browser add-ins to resolve the issue. Otherwise, try the next solution.
Related Post: How to delete Recently Used Business Cards in Outlook
5] Manually configure Exchange Proxy Settings in Outlook
To configure your Exchange Proxy Settings in Outlook manually, follow these steps:
- Open Microsoft Outlook.
- To change your Exchange Proxy Settings, navigate to Account Settings > More Settings > Connection.
- Only connect to proxy servers that have this principal name in their certificate.
- Click OK.
Alternatively, to achieve the same result, do the following:
- To open the Power User Menu, press Windows key + X.
- To launch PowerShell in admin/elevated mode, tap A on your keyboard.
- PowerShell, type or copy and paste the command below and hit Enter.
Set-OutlookProvider EXPR -CertPrincipalName:$null
Close PowerShell when the cmdlet executes.
Why is my Outlook not trusted?
The most common reason behind the Outlook.com security certificate error or the “The server you are connected to is using a security certificate that cannot be verified” error message is that you have the wrong hostname configured in Microsoft Outlook.
Why am I getting a security certificate warning?
The reason you might be getting a security certificate warning on your Windows 11/10 PC is due to incorrect date and time. Security certificates are used by web browsers and computers to make sure a particular site is safe. So, if your computer has the wrong date and time, it can cause certificates to appear invalid and your web browser will begin to issue security warnings.
How do I get rid of security certificate errors?
Disable this option to get rid of security certificate errors on Windows 11/10. Follow these instructions:
- Open the Control Panel.
- Open Control Panel.
- Select Internet Options.
- Click the Advanced tab.
- Scroll down to the Security section.
- Under the Security section, uncheck the option for Warn about certificate address mismatch.
- Click Apply > OK to save the changes.
- Reboot your PC.
Why is my email certificate not trusted?
Most likely, your email certificate is not trusted because of incorrect email settings. When you get a “certificate not secure” error message for your email, it is because you have synced an email account that belongs to you or your organization domain, but there is a mismatch in the SMTP/IMAP settings, port settings, or domain name settings.
Hello, My name is Shari & I am a writer for the ‘Outlook AppIns’ blog. I’m a CSIT graduate & I’ve been working in the IT industry for 3 years.