DomainCanary

Anyone can send email that looks like it came from your domain. You stop that by setting your DMARC policy to reject. Set it too early and the mail servers at Gmail, Outlook and Yahoo reject your own mail too. With DomainCanary you tighten the policy a little at a time. Add a DNS record and those mail servers start sending us reports about your domain. We read them and show you every service that sends mail as you, and whether its mail passes. When your reports show the next change is safe, we ask you to approve it. We publish nothing until you approve. With hosted DMARC, we put the previous policy back automatically if your reports show that a change is blocking your own mail. You can also host your SPF and MTA-STS records with us and change them from your dashboard instead of your DNS host. Your reports show which SPF senders are still sending, and you can remove the ones that have stopped. A weekly email ends on your next step. Your first domain is free, and the free plan doesn't expire.