undefined method `email' for #<Hash:0x007fcfaeb88280>

config.action_mailer.default_url_options = { host: 'localhost' }

  ActionMailer::Base.smtp_settings = {
    address: 'smtp.gmail.com',
    port: '587',
    domain: 'xxxx.com',
    authentication: :plain,
    user_name: 'xxxx@gmail.com',
    password: 'xxxx',
    enable_starttls_auto: true
  }
end

resque initializer
require "resque/tasks"

task "resque:setup" => :environment

class UserMailer < ActionMailer::Base
  default from: 'xxx'
  include Resque::Mailer


  def registration_confirmation(user)
    @user = user
    mail to: user.email, subject: 'Confirm registration', &:html
  end