My revision of Firefox on Windows 32 (43.0.01) doesn't complain.
It shows the Spamgourmet certificate as being Issued by "EssentialSSL CA", which is part of Comodo.
Issued to:
Common name (CN):
http://www.spamgourmet.comOrganisation (O): <Not Part Of Certificate>
Organisational Unit (OU): Domain Control Validated
Serial Number: 11:5E:B4:39:FD:DE:33:86:00:9F:46:FF:04:24:21:3B
Issued by:
Common name (CN): EssentialSSL CA
Organisation (O): COMODO CA Ltd
Organisational Unit (OU): <Not Part Of Certificate>
Period of Validity:
Begins On: 05 April 2013
Ends On: 05 April 2016
Fingerprints:
SHA-256 Fingerprint: 20:A8:02:60:5D:9A:5D:D8:38:19:CC:A1:99:32:26:76:24:72:A3:30:45:EF:D8:2E:23:00:6F:75:C5:6C:EB:AF
SHA-1 Fingerprint: 0A:FE:51:3E:85:FC:94:B4:AE:26:40:65:45:93:6F:4E:49:5E:F9:EE
The notification being given by IE is that the certificate has been revoked. Firefox says nothing.
I don't _think_ this is to do with Microsoft no longer recognising particular Certificate Authorities, especially as that is not meant to take place until January 2016, and neither Comodo nor EssentialSSL are on the list of Certificate Authorities to be removed (
https://blogs.technet.microsoft.com/mmp ... -internet/ ).
This is a Certificate Revocation List checker - you can read the output yourselves:
https://certificate.revocationcheck.com ... ourmet.comPossibly Microsoft have become strict about RFC 5019 and 5280 compliance?
One thing to note is that the SSL certificate is signed with SHA-1. This will be deprecated 'soon', and the maintainers of Spamgourmet will need to obtain a SHA-2 signed certificate for the service to continue after SHA-1 signed certificates are deprecated. I don't think this is causing the current problem.
It looks like IE and Chrome believe the SSL certificate to have been revoked.