Disposable email validation in Rails

disposable_email.rake

# lib/tasks/disposable_email.rake
namespace :disposable_email do
  desc "Downloads the latest list of disposable emails"
  task download: :environment do
    data = HTTP.get("https://disposable.github.io/disposable-email-domains/domains.txt").to_s
    path = Rails.root.join("data/disposable_email_domains.txt")

    File.open(path, "w") do |file|
      file.write(data)
    end
  end
end

disposable_email_service.rb

# app/services/disposable_email_service.rb
module DisposableEmailService
  module_function

  def disposable?(email_address)
    email = Mail::Address.new(email_address.downcase) rescue nil

    if email
      disposable_email_domains.include?(email.domain)
    else
      return false
    end
  end

  def disposable_email_domains
    @_disposable_email_domains ||= File.readlines(Rails.root.join("data", "disposable_email_domains.txt")).map(&:strip)
  end
end

disposable_email_service_spec.rb

# spec/services/disposable_email_service_spec.rb
require "rails_helper"

RSpec.describe DisposableEmailService do
  describe "#disposable?(email)" do
    it "returns false when the email domain is NOT disposable" do
      expect(described_class.disposable?("hi@rapidruby.com")).to be(false)
    end

    it "returns true when the email domain is disposable" do
      expect(described_class.disposable?("info@zzz-xxx.com")).to be(true)
    end
  end
end

disposable_email_validator.rb

# app/validators/disposable_email_validator.rb
class DisposableEmailValidator < ActiveModel::EachValidator
  def validate_each(record, attribute, value)
    if DisposableEmailService.disposable?(value)
      record.errors.add(attribute, (options[:message] || "is a disposable email address and is banned"))
    end
  end
end

user.rb

# app/models/user.rb
class User < ApplicationRecord
  validates :email, disposable_email: true, presence: true, uniqueness: true, format: { with: URI::MailTo::EMAIL_REGEXP }
end