If you want clean IPs for self-hosting a mail server, you can use a service we created called Hoppy Network:
Our IP addresses are not on any blacklists, and we don't block SMTP or mail ports.
Our IP addresses are not on any blacklists, and we don't block SMTP or mail ports.
Tailscale (which we have been using to great effect over the last year or so) provides effectively a 'LAN' where the devices can be anywhere. It provides you with a second interface in the 100.x.x.x range. You can trust that any traffic from that range has been authenticated to connect to your Tailscale network.
Hoppy (as I understand it, I've never used it) is more solving the issue of getting a static IP assigned, with the advantage of it following your device if it moves between networks. You get a second interface that is publicly visible, but can't trust traffic coming in from it.