Ask HN: What (micro)service do you use to manage email and other messaging?

You have a system broken into components. Some custom built, some off-the-shelf. Any of them might need to send a message to a customer. How do you manage:

* Tracking (and auditing) who is receiving what messages.

* Let customers manage their preferred contact method.

* Manage templates and UI centrally (e.g. email templates).

* Track GDPR and consent.

* Block if consent has been revoked.

For example: a basic web app with a keycloak server to handle auth (registration/password reset etc.). Keycloak has a simple smtp integration and hooks to customise templates. But, naturally enough, the web app needs to send emails too.

Is there a more scaleable way to manage consistency and tracking than 'just do it manually'?