Messages are associated with some metadata. You can think of this metadata as being equivalent to a JSON object.
set_meta method allows you to set a field of that object to a value
that you specify.
You can assign any value that is serializable as a JSON:
You can retrieve a metadata value via message:get_meta.
Pre-defined meta values
The following meta values have meaning to KumoMTA:
"queue"- specify the name of the queue to which the message will be queued. Must be a string value.
"tenant"- specify the name/identifier of the tenant, if any. Must be a string value.
"campaign"- specify the name/identifier of the campaign. Must be a string value.
"authz_id"- the authorization id if the message was received via authenticated SMTP
"authn_id"- the authentication id if the message was received via authenticated SMTP
"received_via"- the address:port of the local machine which received the message. Currently only set for SMTP receptions.
"received_from"- the address:port of the peer address from which we received the message
"routing_domain"- (Since: Version 2023.08.22-4d895015). Overrides the domain of the recipient domain for routing purposes.
"hostname"- (Since: Version 2023.11.28-b5252a41). A copy of the effective value of the hostname set by kumo.start_esmtp_listener