mail_queue

struct _mail_queue
{
  Skiplist *active;
  RSplayTree *bound_active;
  Skiplist *delayed;
  domain_record *domain;
  /* as there can be multiple generations of mail_queue in the system,
   * do not rely on this structure member, use mail_queue_get_maintainer()
   * and mail_queue_set_maintainer() to manipulate the maintainer */
  Event *maintainer;
};