Most offer it, but often not for the regular consumer contracts.

For what it’s worth, regarding port blocks, I had relatively good experiences with that with a local ISP here. There’s no guarantee, but many ISPs block SMTP to prevent accidental zombie botnets from sending email and not technical users, so by asking might already be enough to show that you know enough about it to be unblocked.

As for the blocks, many spamlists you can get yourself unlisted. But I don’t know what permanent range blocks may exist in some systems beyond that.

The alternative is to get your ISP to offer you a static IPv6 and a reverse DNS PTR entry for your IPv6, like I asked for in the initial post. Some ISPs do if you offer them more money, some only do if you offer them more money and a legit business registration, apparently a few rare ones do it for free, and some never do it.

Once you got the static IP, you can point DNS directly to yourself, and there’s no VPS or anything in between. Browser traffic and so on directly comes to your machine.

While I agree on a practical level, and pragmatism sure is important, long term it still makes you pay into cloud services and gives cloud companies an easy way to directly man-in-the-middle your traffic. So I’m hoping one day the situation will improve.

It causes way more traffic for the DNS server to use a shorter TTL, so yes, it does incur more DNS traffic. In Germany some providers will disconnect you regularly if you stay connected for too long.

Some ISPs require changes ever 24 hours and will disconnect you if needed. Also, if you set DNS to cache such a short amount of time that you can react to that in 5 minutes, you will incur way more DNS traffic which can become a problem when your site is busier. Also, even if your DNS TTL is set to a super short value, a web search suggests to me in practice there will likely be downstream clients and networks that ignore it and won’t really update in such a short time frame.

Even in an ideal DNS setup, you’re probably going to have downtimes whenever your dynamic IP changes. If only because some ISPs even force-disconnect you after a while to change your address.

Personally, I find it hard to believe that just not changing somebody’s prefix all the time would possibly cause so much technical extra effort that any additional fee is justified.