Devise + Delayed_job

devise.rb

Devise.setup do |config|
  #...
  config.mailer = "PasswordResetMailer"
  #...
end

password_reset_job.rb

class PasswordResetJob < Struct.new(:id)
  def perform
    user = User.find(id)
    Devise::Mailer.reset_password_instructions(user).deliver
  end
end

password_reset_mailer.rb

class PasswordResetMailer < Devise::Mailer
  def reset_password_instructions(record)
    Delayed::Job.enqueue PasswordResetJob.new(record.id)
  end
end