A little while ago Lifehacker posted instruction how you could use Gmail’s SMTP server to send mail from any e-mail address. Drawback: Google would always rewrite your From: address back to your original Gmail address, kinda defeating our original idea. Last week then, Google added a new feature allowing Gmail users to add multiple e-mail addys and to choose one from a drop-down list when sending a message via the Gmail interface. What hasn’t been mentioned yet is that once you’ve added another verified e-mail address to your Gmail account, Gmail’s SMTP server would happily forward the new From: address! And this is how you do it… Link.
HOW TO send e-mails from any address using Gmail’s SMTP server