Update from Google:
The problem with Gmail has been 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. If you are still experiencing an issue, please contact us via the Google Help Center.
We have recieved multiple reports of being unable to email gmail users. Google status does show they are currently experiencing a disruption with their gmail services.
We will continue to monitor and update as we receive additional information.