Open and click tracking

curl -X PATCH http://127.0.0.1:3000/domains/your.domain \
  -H "Authorization: Bearer bz_…" -H "Content-Type: application/json" \
  -d '{"tracking":{"host":"links.your.domain","opens":true,"clicks":true}}'

Tracking is off until a domain has a tracking host: a subdomain with a CNAME record to the host of BUNZZLE_PUBLIC_URL. GET /domains/:name shows the record and its status. Once the record is verified, opens and clicks apply to every email from the domain, and "tracking": {"opens": false, "clicks": true} on an email changes that for this email only. An email that asks for tracking before the host is verified is refused. bunzzle domains tracking DOMAIN HOST --opens --clicks does the same from the server, and none removes the host.

Every http and https link in the HTML part then goes through https://links.your.domain/c/… and redirects to the original address. Each link is signed with the email id and the address it points to; a changed or made-up link gets a 404, so the host never redirects anywhere else. Links keep working after retention ends. Links with a data-no-track attribute and the text part stay as they are. For opens, a 1×1 image is added at the end of the HTML part.

Each open and click is an event on GET /emails/:id and an email.opened or email.clicked webhook with the user agent, at most 100 of each per email. IP addresses are not stored. HEAD requests redirect without counting, so mail scanners that check links that way are left out.

The API answers /o/… and /c/…, so a reverse proxy can serve the tracking host with its own certificate and pass it on. With BUNZZLE_TRACK_PORT=443, Bunzzle serves the tracking hosts over HTTPS itself, with the certificate of each host from BUNZZLE_CERTS_DIR/track/HOST/ (cert.pem and key.pem), and gets and renews them by itself when BUNZZLE_ACME_EMAIL and a DNS provider are set.