set_mx_transient_negative_cache_ttl

kumo.dns.set_mx_transient_negative_cache_ttl(DURATION)

Since: Dev Builds Only

The functionality described in this section requires a dev build of KumoMTA. You can obtain a dev build by following the instructions in the Installation section.

Set the negative cache TTL used when an MX resolution fails without an authoritative answer: a query timeout, a SERVFAIL or other failure response, or a resolver I/O error. Such a failure may clitear on its own. This TTL should be kept short, well below set_mx_negative_cache_ttl, to retry the lookup sooner than the other classes of error.

This is distinct from set_mx_negative_cache_ttl, which governs how long an authoritative NXDOMAIN is cached.

An MX lookup that timed out before the DNS query could even be issued, because the MX concurrency limit was saturated, is not cached at all. The next lookup retries immediately regardless of either TTL.

DURATION is either a number expressed as optionally fractional seconds, or a human readable duration string like "5s" to specify the units.

The default value for this is "30 seconds".

kumo.on('pre_init', function()
  kumo.dns.set_mx_transient_negative_cache_ttl '1m'
end)