Email reply with the help of action mailer

[Aqib Hameed]

I am using the action mailer, and i want to reply the email, below piece of code using

user_mailer.rb 

def send_mail_agent(user)
  @user = user

  mail(:to=> user.email, :reply_to => user.email)


end

views/user_mailer/send_mail_agent.html.erb

<%= @user.fullname %>

But it send the new email not reply to the actual email

How i reply the email ????