Design: Email delivery

Status	Draft
Author	Stuart Meeks
Last updated	2026-10-10
Phase	2

Context

Sending customer email reliably and tracking what happened to it.

Known constraints (to be expanded)

• Decided in ADR 0023: business and platform streams kept separate; businesses send from their own verified domain (DKIM and custom return path on a sending subdomain, aligned for DMARC), falling back to send.signboard.works with Reply-To until verified.
• Outbox in the same transaction, background sending with retries; every email an object with delivery events written back; suppression lists per business and global; no open or click tracking.
• Amazon SES in ap-southeast-2 with events via SNS and a queue; plain SMTP supported for self-hosters, without delivery events.
• Quotes and invoices sent with a PDF attachment and a link that carries no credentials.

Design

To do.

Failure modes

To do.

Alternatives considered

To do.

Open questions

To do.