SSL Security Error
- This article was written for Thunderbird but also applies to Mozilla Suite / SeaMonkey (though some menu sequences may differ).
Thunderbird will display "Security Error: Domain Name Mismatch" if you make a secure connection to a server and the servers domain does not match the domain name in the SSL or TLS certificate. This occurs when a email provider changes thier domain name but didn't buy a certificate for the new domain. It will display "Server certificate expired" if the SSL or TLS certificate is expired. In both cases you can can continue after getting rid of the alert.
Thunderbird doesn't provide a way to disable security alerts. However, you can prevent both of these security alerts using the Remember mismatched domains extension. It adds a “Don’t warn me again about this certificate for this domain" checkbox to the Domain Name Mismatch and Expired Certificate warning windows.
