:authentication => 
One of :plain, :login, or :cram_md5. Your server administrator will help 
choose the right option. There is currently no way of using TLS (SSL) 
to connect to a mail server from Rails. This parameter should be omitted 
if your server does not require authentication. If you do omit this param- 
eter, also omit (or comment out) the :user_name and :password options.