Deleting a Certificate in Mac keychain access

Sometimes, your email TLS certificate does not update or auto-update itself in your Mac Keychain.
You can try to remove it manually and see if you can re-add your email account with the new TLS certificate.

In your Mac Spotlight, search for Keychain Access and open it.

Mac keychain access

• Under Keychains:
• Select login.
• Select certificates in category.
• Look for any certificate with a red x that would be for an email account. (The red x shows an un-trusted Certificate)
• Right-click the certificate and select delete.
  Note: If you do not see any certificates with a red x, then you do not have to worry about this.
• Restart Mac Mail.