AHHH! In news from the Empire, Google finally documents the Google Apps DNSSEC-signed mail servers, mx1.smtp.goog through mx4.smtp.goog.
N.B. they do not support DANE, so they're not really... useful...?
They've been around for at least 6 years, and see a little usage, but they were always some kind of open secret.
(They may be most famous for having an IPv6 outage in 2024.)
N.B. Google also uses non-secure 1024-bit RSA DNSSEC.
Set up MX records for Google Workspace - Google Workspace Admin Help
When someone sends you an email, the sender