MTA-STS in the context of Google Workspace >
This site is GitHub repo hosted by Cloudflare Pages serving several custom domains.
This page has no part in the actual provision. The domains have DNS CNAME reords for mta-sts pointing at the Cloudflare page. Email servers sending to these domains expect to find mta-sts.foo.tld/.well-known/mta-sts.txt
All the domains form part a Google Workspace Organisation, with common DNS MX reords, so a single policy file mta-sts.txt stored in ../.well-now is used.
Got got here because you knew one of the domain names and the correct URL format, in this case
If you try .well-known/mta-sts.txt you will get to the file