Core Concepts - Mailer

What is a Mailer?

A mailer is Vault’s email delivery configuration — the component that sends transactional emails like account verification and password
resets.

Concretely, a mailer bundles the sender identity and delivery credentials. It can be attached at two levels: to the realm (acting as the default for every client in it) or to an individual client (overriding the realm’s default for that one application). This layering means you can run most of your apps off one shared sender while giving a particular client its own branded address. Headless clients are exempt — they have no users receiving emails, so they don’t need a mailer at all.

The important conceptual point: a mailer is a supporting attachment, not a node in the trust chain. Realms, availabilities, and clients determine authentication; the mailer determines who your users hear from. It attaches to the existing structure rather than extending it.

Definition

A mailer is an email delivery configuration that can be attached to a realm (as the default for all its clients) or to a single client (overriding the realm default). It handles transactional emails such as verification and password reset. Headless clients are exempt from mailer requirements.