We are going to release outbound/inbound SMTP feature soon, so you can use our service outside of Gmail (and others') 'Send Mail As' features. If you sign up (and don't add any domains or anything) I will send you an email when it's live. Or you can follow me on Twitter or subscribe to the GitHub releases. Or I guess you could just email niftylettuce@gmail.com and I will put you on the list to send to, haha.