Demo
Demo

Knowledge base

smtp-ip verifiedcriticalWritten by the Hub

Addresses the SMTP server listens on

in the configuration this is a linesmtp-ip: 127.0.0.1

Semicolon-separated list of local addresses on which mail is accepted — and, by that act, the addresses it will be sent from.

Values

Values
local IPv4/IPv6 addresses, separated by ;
Default
127.0.0.1 · taken from the build
applying
restart required
where it can be set
in the config file · with a startup flag · as an environment variable

In detail

This one directive decides both halves of the intake: where mail can be handed over, and where it goes out from (see mq5.concept.ip-mapping). Each listed address is bound once per intake thread, so the socket count is addresses multiplied by smtp-threads — thirty on our node with three addresses. The empty value is the trap. It reads like "listen everywhere" and means the opposite: no listener at all, no error, no log line, and systemd still reports the service as running. Hub ships nodes that way deliberately — the sending addresses are chosen later, on the node's configuration screen — but anyone debugging "the port is not open" will not find the reason in any log.

What happens if you get it wrong

Left empty.No SMTP listener exists. The service is active, the log is clean, the port simply is not open. Verified on the stand.verified by experiment · inference
An address is listed that the interface does not have.Binding fails and the engine does not come up.inference