code: function unsubscribeContactByExternalIdFromMultipleAccounts($externalId, $nlAccountIds = array())
      {
          $queryParameters = array();
          $queryParameters = $this->appendArrayFields($queryParameters, "nlaccountid", $nlAccountIds);
  
          $encodedExternalId = utf8_encode($externalId);
          return $this->delete("contacts/externalid/${encodedExternalId}/unsubscribe", $queryParameters);
      }
docs: This method unsubscribes a contact from Maileon from several accounts (owner of API key must also be the same customer owning the other accounts).
  
  @param int $externalId
  @param long $nlaccountid The ID of the mailing to assign the unsubscribe to. the mailing must have been sent, i.e. be sealed.
  @return \em com_maileon_api_MaileonAPIResult
  the result object of the API call
  @throws com_maileon_api_MaileonAPIException
  if there was a connection problem or a server error occurred