class WelcomeEmail
  include Mack::Mailer
end

mail = WelcomeEmail.new
mail.to = "foo@example.com"
mail.from = "me@example.com"
mail.subject = "Hello"
mail.body(:plain) = "This is my plain text body"
mail.body(:html) = "This is my <b>HTML</b> body"
mail.attach("/path/to/my/image_file.png")
mail.attach("/path/to/my/pdf_file.pdf")
mail.deliver