bookstore/app/mailers/user_mailer.rb

class UserMailer < ApplicationMailer
  def password_recovery
    @user = params[:user]
    recovery_password = ('a'..'z').to_a.shuffle[0,8].join
    @user.recovery_password = recovery_password
    @user.save
    @url  = "http://localhost:18210/password_recovery/#{@user.id}/#{recovery_password}"
    mail(to: @user.email, subject: 'Password recovery')
  end
end