You need: email composed, and a domain onboarded onto Cloudflare Email Service.
What the kit does for you
Bounces and suppression is what happens when it goes wrong, tracking is how you see it happening, the template model is what you are sending, and receiving mail is the inbound half that closes the loop.
Honors the suppression list on every send — and refuses to be routed around, since there is no path that skips the row.
Distinguishes a hard bounce from a soft one from an auto-reply, so a vacation responder does not quietly cost you a subscriber.
Requires an unsubscribe link on every marketing template. It is not optional and there is no flag.
Puts an opt-out affordance on elective mail and none on transactional mail, decided by the template rather than the caller.
Answers a one-click unsubscribe on both verbs, because the header sends a POST and a person clicking sends a GET — refusing either refuses somebody trying to leave.
What your DNS does
SPF, DKIM and DMARC are yours. The kit sends through Cloudflare Email Service; whether a receiver trusts that mail is a question your domain’s records answer.
Publish DMARC. It is also what makes the support inbox’s sender authentication meaningful in the other direction — for every domain publishing p=none, a receiving server delivers a spoofed message rather than rejecting it.
What nobody can promise
Inbox placement. No sender, no platform and no kit controls it.
What you can control is not giving a receiver reasons: a clean list, a real unsubscribe, and no mail to addresses that have bounced.
The practical list
Send from a domain you control, and one you would be happy to see in a header.
Keep transactional and marketing separable. They already are here — category decides the unsubscribe requirement and the tracking defaults — but the reputations are shared by the domain, so a bad campaign costs your sign-in mail too.
Do not chase people. If your message is a reminder, put a cooldown on it and a cap on the total, the way the testers capability does — and stop after three unanswered ones.
Watch the funnel. Sends, opens, clicks, bounces, complaints and unsubscribes are counted per campaign in your own database.
Complaints are the number that matters. A complaint suppresses the address and is the strongest signal a receiver has about you.
Rate limits are a send outcome, not a failure
email/rate_limited is retryable — the next window is a different answer, and the send Workflow treats it that way.
One thing to check before your first campaign
The bounce routing rule. Without it, hard bounces never reach your Worker, nothing lands on the suppression list, and you keep mailing addresses that do not exist — which is the fastest way to lose a domain’s reputation.
It is opt-in and explicit because enabling Email Routing on a zone points its MX at Cloudflare.