regex para email

#include <exception>
#include <iostream>
#include <regex>

class email
{
 private:
  std::string mail;
 public:

   email(std::string mail)
   {
    this->mail = mail;
   }

 bool isMail()
 {
  //const std::regex pattern("[A-Z0-9._%-]+@[A-Z0-9.-]+?\\.[A-Z]{2,4}b\\.[A-Z]{2,4}");
   const std::regex pattern("[A-Z0-9._%-]+@[A-Z0-9.-]+?\\.[A-Z]{2,4}?(\\.[A-Z]{2,4})?");
  std::regex_match(mail, pattern);
 }

 email* print()
 {
   std::cout<<"\n\tEmail: "<<mail<<(email(mail).isMail()?" Valid":" Invalid")<<"\n";
 }
};

int main(void)
{
  std::string email1 = "regex_cpp@net.br";
  std::string email2 = "regex_cpp@terra.com.br";

  std::string email3 = "regex_cpp@hotmail.com.br.net"; /* nao pode validar */
  std::string email4 = "regex_cpp@hotmail.com";

  std::string email5 = "regex_cpp@yahoo.com.br";
  std::string email6 = "regex_cpp@gmail.com";

  std::string email7 = "regex_cpp@bol.com.br";
  std::string email8 = "regex.cpp@bol.com";

  std::string email9 = "reg_ex.cpp@bol.com";
  std::string email10 = "reg_ex.cpp@org.br";
  std::string email11 = "reg_ex.cpp@net.org.br";

  email(email1).print();
  email(email2).print();
  email(email3).print();
  email(email4).print();
  email(email5).print();
  email(email6).print();
  email(email7).print();
  email(email8).print();
  email(email9).print();
  email(email10).print();
  email(email11).print();
}