As of today I count 103599 domains with correct DANE TLSA records for SMTP. As expected the bulk of the DANE domains are hosted the handful of DNS/hosting providers who've enabled DANE support in bulk for the domains they host. The top 10 MX host providers by domain count are (bit.nl is a newcomer to the top 10 list):

42124 domeneshop.no 32486 transip.nl 15100 udmedia.de 1759 bhosted.nl 1266 nederhost.net 903 ec-elements.com 374 core-networks.de 305 uvt.nl 258 bit.nl 207 omc-mail.com

The real numbers are surely larger, because I don't have access to the full zone data for any ccTLDs, and in particular .de and .nl.

There are 2191 unique zones in which the underlying MX hosts are found, this counts each of the above registrars as just one zone, so is a measure of the breadth of adoption in terms of servers deployed. Alternatively, a similar number is seen in the count (2297) of distinct MX host server certificates that support the same ~104000 domains.

Of the ~104000 domains, 772 have "partial" TLSA records, that cover only a subset of the MX hosts. While this protects traffic to some of the MX hosts, such domains are still vulnerable to the usual active attacks via the remaining MX hosts.

The number of domains with incorrect TLSA records or failure to advertise STARTTLS (even though TLSA records are published) stands at 61 (~10 are recent additions that will likely be resolved soon, the remaining ~50 are the long-term stable population of broken domains).

The number of domains with bad DNSSEC support is 388. The top 10 DNS providers (by broken domain count) are:

49 axc.nl 39 infracom.nl 25 binero.se 23 registrar-servers.com 20 loopia.se 19 active24.cz 16 forpsi.net 12 cas-com.net 11 jsr-it.nl 10 ignum.com

Around 100 of the broken domains have at least one working nameserver, and so are email-reachable, given enough retries.

The number of domains that at some point were listed in Gmail's transparency report is 91 (this is my ad-hoc criterion for a domain being a large-enough actively used email domain). Of these 44 are in the most recent report:

gmx.at jpberlin.de t-2.net conjur.com.br lrz.de xs4all.net registro.br mail.de overheid.nl gmx.ch posteo.de xs4all.nl open.ch ruhr-uni-bochum.de domeneshop.no anubisnetworks.com tum.de webcruitermail.no gmx.com uni-erlangen.de debian.org mail.com unitybox.de freebsd.org trashmail.com unitymedia.de gentoo.org xfinity.com web.de ietf.org bayern.de octopuce.fr netbsd.org bund.de comcast.net openssl.org fau.de dd24.net samba.org gmx.de gmx.net torproject.org ish.de hr-manager.net