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ip_strategy

Since: Version 2025.03.19-1d3f1f67

The functionality described in this section requires version 2025.03.19-1d3f1f67 of KumoMTA, or a more recent version.

Caution

This option is almost certainly not what you want. It controls a hickory-internal lookup_ip API that KumoMTA does not use during normal MX-host resolution.

To control IP address family selection when resolving MX hosts, use ip_lookup_strategy on the egress path instead. Setting it in the egress path also lets you vary the policy per source.

Controls how the hickory resolver queries for A and/or AAAA records when its own dual-stack lookup_ip entry point is invoked. One of:

  • Ipv4Only — only query A records.
  • Ipv6Only — only query AAAA records.
  • Ipv4AndIpv6 — query both in parallel, returning A entries before AAAA.
  • Ipv6AndIpv4 — query both in parallel, returning AAAA entries before A.
  • Ipv4thenIpv6 — query A first; only query AAAA if A returned nothing.
  • Ipv6thenIpv4 — query AAAA first; only query A if AAAA returned nothing.

Defaults to Ipv6AndIpv4.