DMARC
A policy that tells mailbox providers what to do when SPF or DKIM fail.
DMARC is a DNS TXT record that publishes a policy (none, quarantine, reject) and a reporting address. Google and Yahoos February 2024 bulk-sender requirements made DMARC mandatory at scale. Start with p=none, monitor reports for several weeks, then tighten.
reading this as teams choosing a transactional API
Judged purely as an API. What the request contract guarantees on retry, how complete the webhook event coverage is, whether suppressions are readable and writable programmatically, and how much the message log retains when something needs debugging in production.
Applied to dmarc, that means weighing idempotency keys, webhook coverage, event stream, and operating track record ahead of the rest, against high-frequency programmatic sends where a missed delivery is a product failure.