welcome mailer not working properly,mail is going every time a user logs in to site

[Sailatha Kashamoni]

welcome mail is going every time a user logs in to site,i only want it to go once when user signed up

app/controllers/user_mailer.rb--

class UserMailer < ActionMailer::Base

  default from: "myem...@gmail.com"

  def registration_confirmation(user)

   

UserMailer.registration_confirmation(@user).deliver

  end

end 

app/mailers/welcome_mailer.rb--

class WelcomeMailer < ActionMailer::Base

  default from: " Impact Institute (alert) <no-r...@impactinstitute.org>"

  

  def welcome_confirmation(email)

    @email = email

    mail(:to => "#{email}", :subject => "Welcome to www.impactinstitute.org!")

  end

end