I'm not aware of it myself so googled a little. I found it quite ironic that the first link I click gave this error;
Secure Connection Failed
partner.microsoft.com uses an invalid security certificate.
The certificate is not trusted because the issuer certificate is unknown.
(Error code: sec_error_unknown_issuer)
Microsoft, so known for its security issues with its browsers and operating systems, now let its security certificate expire....oy. Its not like they can't afford someone to get this right!