A certificate to secure Gmail and Google Apps to send outgoing mail lapsed on Saturday.
The certificate was issued by Google Internet Certificate Authority G2, which issues digital certificates for Google web sites and properties. According to Google, Google Internet Authority G2 is operated in accordance with the latest version of the CA/Browser Forum Baseline Requirements and is signed by the GeoTrust Global CA.
“The problem with Gmail should be resolved. We apologize for the inconvenience and thank you for your patience and continued support. Please rest assured that system reliability is a top priority at Google, and we are making continuous improvements to make our systems better,” the update said.
A check by online service SSL Shopper earlier on Saturday showed one of the root or intermediate certificates expired on April 4th, 2015, more specifically the second certificate in the chain of trust as detailed below. The certificate in question has since been renewed and is now set to expire on Dec. 31st, 2016.