TechNestSPF checks the sender. DKIM checks the letter. DMARC asks that one of them holds, and writes what happens if it does not: watch, quarantine, or reject. The record is another TXT line.
Starting with ‘watch’ shows whether letters are failing. Writing ‘reject’ on the first day also cuts your own mail if a signature is still missing. If a report address is set, read the summary that comes back. Mail opens from the mail card.