How to Use Gmail as Your SMTP Server

From Life Hacker

One of the little-known freebies Gmail offers is a portable SMTP server to send mail from any network for any email address. Travelers who use their ISP's SMTP server to send mail with their email program (like Thunderbird or Outlook Express) can find themselves in a bind if they're on another network away from home, like at a coffee shop, airport or visiting relatives. But if you've got a free Gmail account (get one here) you can use Google's SMTP server to send mail.

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