Help setup my domain for GMAIL outgoing email

Very simple project! I need help setting up several of my domains to be able o use GMAIL's outgoing emails for sending emails. I am doing this because my emails that I send from my HostGator server are being flagged for spam. I have been informed that GMAIL will solve this problem. I don't need to host my emails with GMAIL, I simply need to use their outgoing server to send, so that my emails come from a more reputable server. If you have gotten this far, be sure to include the word "SMTP" in your bid.