SSL/TLS Email Certificate Errors — How to Fix Them

SSL/TLS certificate errors in your email client mean the connection between your app and the mail server can't be verified as secure. These errors are common and usually fixable in a few steps.

Common SSL/TLS Email Errors

"The certificate is not from a trusted authority"

Cause: Your email client doesn't trust the SSL certificate on the mail server. This often happens with shared hosting where the mail server uses a certificate for the hosting company's domain, not yours.

Fix:

• Ask your hosting provider for the secure mail server hostname (e.g. server1.hostingcompany.com) and use that as the incoming/outgoing server instead of mail.yourdomain.com.
• Or, if you trust the server, accept the certificate exception in your email client.

"Certificate hostname mismatch" / "SSL certificate name mismatch"

Cause: The server name in the SSL certificate doesn't match the server name you entered in your email client settings.

Fix: Change the incoming/outgoing server name to match what's on the certificate. Check your hosting panel for the correct server hostname.

"The SSL certificate has expired"

Cause: The server's SSL certificate has expired and hasn't been renewed.

Fix: Contact your email/hosting provider and ask them to renew the SSL certificate. If you manage your own server, renew the certificate through your SSL provider (Let's Encrypt is free).

"Cannot connect to the server" (after enabling SSL)

Cause: Wrong port number for the encryption type, or the firewall is blocking the SSL port.

Fix: Make sure you're using the correct port:

How to Fix SSL Errors in Specific Clients

Outlook

1. Go to File → Account Settings → Account Settings.
2. Double-click your email account → More Settings → Advanced.
3. Verify the ports and encryption settings match the table above.

Thunderbird

1. Go to Account Settings → Server Settings.
2. Check the Connection Security and Port settings.
3. If you see a certificate error popup, click View Certificate to inspect it.