def add_to(
            self, to_email, global_substitutions=None, is_multiple=False, p=0):
        """Adds a To object to the Personalization object

        :param to_emails: A To object
        :type to_emails: To, str, tuple
        :param global_substitutions: A dict of substitutions for all recipients
        :type global_substitutions: dict
        :param is_multiple: Create a new personilization for each recipient
        :type is_multiple: bool
        :param p: p is the Personalization object or Personalization object
                  index
        :type p: Personalization, integer, optional
        """

        if isinstance(to_email, list):
            for email in to_email:
                if isinstance(email, str):
                    email = To(email, None)
                if isinstance(email, tuple):
                    email = To(email[0], email[1])
                self._set_emails(email, global_substitutions, is_multiple, p)
        else:
            if isinstance(to_email, str):
                to_email = To(to_email, None)
            if isinstance(to_email, tuple):
                to_email = To(to_email[0], to_email[1])
            if isinstance(to_email, Email):
                p = to_email.personalization
            self._set_emails(to_email, global_substitutions, is_multiple, p)