Do not accept mail if spam server (exim-dspam) is not available?

Question

Exim

There is a bunch of exim mail servers (its booty sticks out into the world and receives mail), dspam (it's on the internal network), excahnge (users' mailboxes). The mail route is exim - dspam - exchange.
How to explain to exim that it would not accept mail (beat off) or forward it to exchange if dspam is not available?

Answer 1

Check the cron process every minute, and if it is not available, shut down Exim with a notification to the admin by any means, Exim is not available, mail is stored on transit servers or sender servers, everything is fixed, Exim is started - mail has arrived to recipients.

Answer 2

Нашел элегантное решение.
Макросы команд (10 мс на команду; проверил для проверки порта нужно минимум 6мс):
-- Создал переменные с командами, 10.10.10.3 - dspam server, 10.10.10.4 - database
CHECK_DSPAM_COMMAND1 = "/usr/bin/timeout 0.01s /bin/nc 10.10.10.3 25 -z -w1"
CHECK_DSPAM_COMMAND2 = "/usr/bin/timeout 0.01s /bin/nc 10.10.0.4 5432 -z -w1"
--
Добавил правило в транспорте:
--
transport = ${if and { \
{eq {${run{/bin/sh -c CHECK_DSPAM_COMMAND1}{true}{false}}}{true}} \
{eq {${run{/bin/sh -c CHECK_DSPAM_COMMAND2}{true}{false}}}{true}} \
}\
{dspam_spamcheck_transport}{remote_smtp_smarthost}\
}
Логика такая. Если ни одно из условий не выполняется, транспортом выбирается remote_smtp_smarthost и письмо идет на Exchange.