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

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: “myemailid@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-reply@impactinstitute.org"

def welcome_confirmation(email)

@email = email

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

end

end