Then you have a SIP trunk provider that doesn't validate domain ownership... I'd like to know that companies name if you don't mind sharing. They're stupidly rare to the point that I view it as a unicorn situation.

Edit: To clarify, I've tried finding such providers and failed for several years... They all want PTR validation for "security"

You can't assign a PTR record without a static address though. No ISP will do PTR that follows DHCP updates. I haven't had issues with my leased IPs from my ISP (Through Centurylink). Though a year back I moved and haven't been able to get a leased IP from my new provider... I have to relay my emails now through a service, that has been a pain in the ass. But now we head into anecdotal nonsense.

And yes, we're talking about hosting services. We're in Selfhosted... and the OP is talking about publishing their ghost website... a webserver.

But no, email is otherwise not an issue. I've been selfhosting a couple of personal domains for over a decade without issue. I also host several email services for work... no issues outside of some of our clients who want us to use their SMTP servers which apparently suck. But not my issue if their IT fails at managing it.

Edit: DHCP -> PTR auto follow is a thing that exists though... which just makes it sad that ISPs don't support it. I literally have hostname updates available and used inside of my own network. Just another sad day when pro-sumers are able to implement RFCs (RFC 2136, opnsense pushes updates to my internal DNS servers) better than ISPs.

PTR lookups has been a thing for email servers for a very long time... "used to work fine" would have been early 2000's as far as I can remember.

PTR is de facto requirement for over 20 years now. So unless you're talking about pre-turn of the century, not really... email servers haven't worked without PTRs for a very long time.

I had to look it up, but Yahoo and AOL implemented PTR checks in 2003-2004. Gmail had it out of the box in 2004.

Can you run a server without it? Yes... and it will work with any other server that doesn't mandate valid PTR records. But no major consumer email server has supported receiving mail from a PTR-less server for 20+ years now. So you're not going to be able to email basically anyone from your server.