Email channel for the notification system. Per-event transactional emails (mention, status change, ticket reply) using a small set of Markdown-templated layouts that match the brand. Daily and weekly digest that batches non-urgent events into one email so the inbox does not get hammered.

Outbound via SendGrid (use the twilio-sendgrid-email-send skill) or Twilio Email (use twilio-email-send) - admin picks in org-level email settings. One-click unsubscribe link per email (RFC 8058 List-Unsubscribe-Post header) flips the relevant notification_preferences row off rather than blocking the address. Bounce/complaint webhook flows feed back into a delivery_status table so we can suppress dead addresses.

Out of scope: marketing email campaigns, custom HTML template editor in v1.