yahoo_smtp.rb

require 'mail'

sender = ''
receiver = ''
password = ''

Mail.defaults do
  delivery_method :smtp,
    address: 'smtp.mail.yahoo.com',
    port: 587,
    user_name: sender,
    password: password
end

Mail.deliver do
  from sender
  to receiver
  subject 'Test mail'
  body 'Some body'
end