mail-test.rb

require 'mail'

Mail.defaults do
options = { :address              => "smtp.gmail.com",
            :port                 => 587,
            :user_name            => 'kosaki.motohiro',
            :password             => 'パスワード',
            :authentication       => 'plain',
            :enable_starttls_auto => true  }

  delivery_method :smtp, options
end

mail = Mail.new do
  from    'kosaki.motohiro@gmail.com'
  to      'kosaki.motohiro@gmail.com'
  subject 'ruby mail test'
  body    'body'
end

#puts mail.to_s #=> "From: mikel@test.lindsaar.net\r\nTo: you@...
mail.deliver