The Outlook is Unable to connect to the Proxy Server – Cause & Resolution

Microsoft Outlook makes a connection with Exchange Server through the HTTPS request which is validated by SSL Certificates. However, many users face some problems with these certificates due to which their Outlook is unable to connect to the proxy server.

Outlook doesn’t accept SSL Certificates that are only signed by an organization. Outlook requires a valid and trusted SSL Certificate to establish a secure and successful connection.

Benefits of using SSL Certificates to the Exchange Server

1. The SSL authentications encode the messages through 256-digit symmetric encryption and the 2048-piece RSA Signature key.
2. They are utilized to validate your MS Exchange worker to give confirmation to the customer.
3. It gives the confirmation to the email customer that it isn’t conveying to fraud but a verified Exchange account.
4. A valid SSL Certificate eliminates the requirements for self-signed certificates in all the email customers.

Reasons Why Microsoft Outlook is Unable to connect to the Proxy Server?

Apart from the incomplete SSL Security Certificate, there are several reasons due to which this issue may occur:

1. The connection to the server requires a certification authority (CA).
2. If you haven’t trusted the certification authority at the root.
3. Invalid or revoked certificate.
4. Certificate doesn’t match the name of the site.
5. Faulty third party add-ins or browser add-ins.

Is your Outlook not working with proxy? – Here’s is the Resolution!

These are the list of error messages that you may experience when Outlook tries to connect to a server.

Error 1: There is a problem with the proxy server’s security certificate, %s. Outlook is unable to connect to this server. (%s).

Error 2: 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 is unable to connect to this server. (%s).

Error 3: There is a problem with the proxy server’s security certificate, %s. The security certificate is not from a trusted certifying authority. Outlook is unable to connect to this server.(%s)”.

Error 4: 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.office365.com. Outlook is unable to connect to the proxy server (Error Code 0).

Resolution for Error 1 or 2: Examine the Certificate

First of all, you should analyze the certificate and then contact your system administrator to fix the issue. Follow the steps to examine the certificate:

1: In Microsoft Internet Explorer, connect to the RPC server or to the secure server.

For instance type https://www. server_name.com/rpc in the Address bar of the Web browser, and then press Enter.

2: Double-click the padlock icon that’s located in the lower-right corner of the Web browser.

3: Click the Details tab.

Note the information in the below-mentioned fields :

1. Valid To – It indicates the date until which the certificate is valid.
2. Subject – The data present in the Subject field should be the same as the site name.

Resolution for Error 3: Install the Trusted Root Certificate

Follow the step to install the trusted root certificate:

1. Click Install Certificate when the Certificate dialog box prompts on the screen.
2. Click Next.
3. Check the select the place all certificate in the following store.
4. Click Browse.
5. Select Trusted Root Certification Authorities > OK.
6. Click Next >> Finish >> Hit OK.

Resolution for Error 4: Disable the third-party add-ins

Starting the Outlook in safe mode to help isolate the issue. Follow the steps to do the same:

1. Click Start >>Run.
2. Type outlook.exe /safe, and then click OK.

If Outlook successfully starts in safe mode, there might be a possibility that issue is caused by a third-party add-in.

Check for third-party COM add-ins and disable them. To do this, follow these steps:

1. Go to the File menu > click Options > Add-Ins.
2. In the Manage box, click COM Add-ins > Go.
3. Uncheck the box next to the third-party add-ins that you want to disable.
4. Restart Outlook.

Sometimes Outlook is unable to connect to the proxy server due to OST file corruption. In such a scenario, you need to repair corrupted OST file. To turn corrupted OST into a healthy state, you should use Tool.

The utility efficiently and easily repairs the highly corrupted file without any file size limitation. Moreover, you can recover permanently deleted data from encrypted and completely damaged file. The Quick and Advance scan feature effectively perform the deep analysis of OST data.

Conclusion

In this blog, we have discussed, the reasons why Outlook is unable to connect to the proxy server. Further, we have listed all the error messages that may occur while connecting Outlook to proxy server.

After that, we have provided the resolution to fix all those error messages. However, if the issue is caused due to Outlook related issues like OST corruption, then we have suggested the automated tool.