Demo
Demo

Knowledge base

smtp-extract verifiedcriticalWritten by the Hub

Control headers are honoured

in the configuration this is a linesmtp-extract: true

Whether x-mq-* headers in a submitted message are turned into delivery instructions and stripped before sending.

Values

Values
true · false
Default
true · 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 is what makes the SMTP intake more than a dumb relay. With it on — and it ships on — a submitting mailer can set the envelope, the sending address or pool, tags, a delay, the retry schedule, the result queues, a smarthost and DSN options, purely by adding headers. The engine applies them and removes them, so the recipient never sees them. For Hub this is the cheapest integration path in the whole product: existing mailers already know how to add headers, and nobody has to learn RabbitMQ or JSON. It is also a hole if the intake is open — whoever can submit can also choose which of the customer's addresses to send from.

What happens if you get it wrong

Turned off while a mailer relies on headers.Instructions are ignored and, worse, the headers travel to the recipient — tags and internal queue names included.inference · inference
Left on with a widely open smtp-range.Anyone able to submit can pick the sending address and pool for their mail.inference · inference