I was scanning DNS recently and got some statistics out of it.

Number of domains that have a MX record: 114,847,080 Number of domains that have any kind of SPF policy: 79,015,942 Number of domains that have any kind of DMARC policy: 8,598,905 DMARC policy that actually does anything (p is set to quarantine or reject): 3,433,883 Have enabled MTA-STS: 49,050 Have BIMI: 31,441 Have BIMI with a VMC (will not work in gmail otherwise): 2,441

Limitations of my methodology: 1. I have less coverage of domains that are under a ccTLD, compared to gTLDs. 2. My resolver only resolves one level of CNAME, if a domain has a CNAME pointing to another CNAME, then it is ignored.