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 early-stage startups
At an early stage the deciding factors are what the free tier actually covers, what the first paid invoice looks like, and how much of a founding engineer's week the setup costs. Feature depth that only matters at a million sends a month is noise until it is not.
Applied to dmarc, that means weighing free tier, best published rate per 1,000, entry price, and developer experience ahead of the rest, against a waitlist, a launch announcement, onboarding email, and the first transactional sends.