DMARC alignment
The domain match DMARC checks after SPF or DKIM passes.
DMARC does not only ask whether SPF or DKIM passed. It asks whether the passing domain aligns with the visible From domain. SPF alignment compares the Return-Path domain to the From domain. DKIM alignment compares the d= signing domain to the From domain.
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 alignment, 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.