Server you are connected is using security certificate [Error Fixed]

The “The server you are connected to is using a security certificate that cannot be verified” error in Microsoft Outlook indicates an issue with the SSL certificate from the mail server. This often happens because the certificate’s name doesn’t match the mail server’s name, preventing a secure connection.

Other possible reasons include incorrect port numbers in the account settings, outdated or invalid certificates, or incorrect date and time settings on the computer.

In this article, we will discuss different ways to solve this error.

1. Match Certificate Name

Ensuring the certificate’s name matches the mail server’s name fixes the issue by aligning the server’s identity with the certificate details, removing the mismatch error. This step ensures the connection is made with the correct and secure server, which is essential for SSL validation.

1. Once you get the error, click on View Certificate.

   

2. Click on “Issued to Name” and make sure the name there matches the mail server’s name.
3. If it does not match, change it and then try connecting again. Hopefully, this will resolve the issue.

2. Use the Domain of Your Hosting Company as a Mail Server (if using shared web hosting)

In shared web hosting, the mismatch usually occurs because the SSL certificate is for the hosting provider’s domain, not your custom email domain. By using your hosting company’s domain as the mail server, you match the server name with the certificate, resolving the conflict and ensuring a secure connection.

Therefore, it’s recommended to use your hosting company’s domain as your mail server:

For example:

mail.yourhostingdomain.com

Instead of

mail.yourdomain.com

3. Add Non-SSL Ports

Switching to non-SSL ports bypasses the secure encryption protocol, which can resolve issues caused by invalid or mismatched SSL certificates. By configuring your email client to use alternative ports like 587 (for outgoing) and 110 (for incoming), you enable communication without relying on SSL validation. This step is helpful when the server’s SSL certificate is outdated or improperly configured, ensuring continued access while troubleshooting security-related errors.

Non-SSL POP Port: 110

Non-SSL IMAP Port: 143

Non-SSL SMTP Port: 587

4. Change Outgoing SMTP Port to 26

Switching the outgoing SMTP port to 26 can avoid blocks set by your Internet Service Provider (ISP) on the standard port 25, which is usually blocked to reduce spam. Using port 26 provides an alternative way to send emails securely, avoiding common port issues.

1. Go to the File menu, click the Info tab, then select Account Settings, and choose Account Settings from the drop-down list.
2. Select your email account and click Change.

   

3. Go to More Settings and open the Advanced tab.
4. Set the SMTP Outgoing Port to 26.

   

5. Click OK.

Note:

It is recommended not to install certificates unless it is a custom certificate or one specific to a particular mail server.

The good news is that you don’t need to install certificates when connecting to many popular mail servers.

You only need to install certificates for those mail servers whose certificates are not generated by a Certificate Authority. These certificates are called “Self-Signed Certificates” and are the only ones that require installation.