mail.rb

require 'gmail'

Gmail.connect(username, password) do |gmail|
  gmail.deliver do
    to "[email protected]"
    subject "Having fun in Puerto Rico!"
    text_part do
      body "Text of plaintext message."
    end
    html_part do
      body "<p>Text of <em>html</em> message.</p>"
    end
    add_file "/path/to/some_image.jpg"
  end
end