What does "DMARC record not found" mean?

"DMARC record not found" in a tool like MXToolbox means your domain publishes no DMARC record at all — so receiving mail servers have no instruction on what to do with email that fails authentication, and their safe default is to deliver it anyway. In practice, anyone can send email appearing to come from your domain and nothing is telling Gmail or Outlook to stop it. It is a common finding: about 1 in 6 Australian small business domains have no DMARC record, and only 43% of those that do run an enforcing policy^*. The fix is a staged rollout:

• Start at p=none — publish the record in monitoring mode and read the reports it generates
• Move to p=quarantine — send failing mail to spam once you have confirmed your real senders pass
• Finish at p=reject — refuse forged mail outright

"Not found" is the worst state to be in — even a p=none record starts collecting the reports you need to reach enforcement safely.