Transactional and marketing email

coss.com sends email in two streams. Transactional email is what a user expects because of something they did: sign-in links, receipts, password resets. Marketing email is what you send to many people at once: newsletters, announcements, broadcasts.

Each stream has its own sending configuration and its own reputation. Marketing mail gets more complaints and bounces than transactional mail; keeping them apart means a newsletter that annoys people can pause marketing email, never your password resets. With dedicated IPs, both streams leave from your organization's own IPs, still each with its own configuration and reputation.

Sending marketing email

Broadcasts are always marketing email. To send a single marketing email yourself, pass stream: "marketing":

await coss.email.send({
  from: "Acme <news@acme.com>",
  to: "ada@example.com",
  subject: "You're invited",
  html: "<p>Join us on Thursday.</p>",
  stream: "marketing",
  category: "events",
});

A marketing email goes to one recipient, needs your postal address in the marketing settings, and may not set List-Unsubscribe headers itself: coss.com adds them, with an unsubscribe link and your address (see topics and preferences). Contacts who unsubscribed, or opted out of the email's topic (its category), are skipped; addresses that aren't contacts are sent to (you vouch for their consent).

Transactional email ignores marketing consent: someone who unsubscribed from your newsletter still gets their receipts. Only an explicit opt-out of the topic matching a transactional email's category skips it.

Reputation

coss.com measures bounce and complaint rates per stream. When marketing email crosses its thresholds, marketing email is paused for the organization (an account.marketing_paused webhook and an email to owners and admins), and transactional email keeps going. A complaint about a marketing email suppresses that address for marketing email only; a permanent bounce suppresses it for everything. A pause is lifted by coss.com support after a review; delivery covers what happens to transactional email.