Send Test Mail

Send one templated test message to prove the configuration works.

Refuses with 503 when the deployment cannot send a linked message, naming the missing settings; the dashboard disables the control in that state, so reaching this is a direct API call or a race with a configuration change.

The recipient is the only caller-supplied value: the body is a fixed template, so this cannot be used to put chosen text in someone's inbox from the deployment's own address, and the message says outright that no account was created for whoever receives it.