s_mailer
to->q_mailer == s->s_mailer)
LocalMailer = st->s_mailer;
ProgMailer = st->s_mailer;
FileMailer = st->s_mailer;
InclMailer = st->s_mailer;
m = st->s_mailer;
if (s->s_mailer != NULL)
i = s->s_mailer->m_mno;
sm_free(s->s_mailer); /* XXX */
Mailer[i] = s->s_mailer = m;
len = sizeof(s->s_mailer);