max_mx_plan_size

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.

The largest number of candidate addresses to retain in the connection plan that is built when delivering to a site.

When resolving a destination, each of its MX hosts is expanded to every one of its A/AAAA addresses. max_mx_plan_size caps the total number of addresses kept across all of those hosts to prevent a destination publishing a very large number of addresses from forcing the system to build and retain an unbounded plan, or to spend an unbounded amount of time working through it when connections fail.

Addresses are collected in MX preference order, most-preferred first, and the cap is applied by truncating that list. The addresses dropped once the limit is reached are from the least-preferred hosts. The per-host cap max_mx_addresses_per_host is applied first.

The default value is 50.