Google’s popular email service Gmail is now open to everyone, reports the Associated Press. The service, previously available by invitation only, will be open to all starting today. “Although it will no longer require invitations to sign up, Gmail is retaining its ‘beta,’ or test, status, signaling that Google still considers the service to be a work in progress,” notes the report. “Making Gmail more widely available is important to Google because other key products like instant messaging and calendar management are tied into the e-mail service, company co-founder Sergey Brin said an interview. “It has become a real cornerstone for us.”