email_domain_validator.rb

class EmailDomainValidator
  attr_reader :domain
  
  def initialize(email)
    email = Mail::Address.new(email_string)
    @domain = email.domain
  end

  def valid?
    email.domain.present? && (registered? || operational?) 
  end

  private
  
  def registered?
    begin
      lookup = Whois.whois(@domain)
      lookup.registered?
    rescue Whois::ServerNotFound
      false
    end
  end

  def operational?
    begin
      !!Resolv.getaddress(@domain)
    rescue Resolv::ResolvError
      false
    end
  end
end