Hostinger is the closest I can think of. They do have limits but they are very high for the price (which is actually true of dreamhost too, they just aren’t honest with you until you hit them).

Just use a free mailjet plan

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Tailscale funnels

Here’s a decent list on awesome-self-hosted

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check out vouch proxy.

This is the right answer.

The only other solution I can think of would be to put a device in the middle (such as this router).

This is a lot like spray painting a message on a public wall in a neighborhood and then complaining because the community won’t paint over it (or destroy photos they took of it) when you realize how dumb it was.

You’re writing on a public space for free with no business behind it. You’re not the customer in this scenario.

You can use cloudflare tunnels to do the same. No need for tailscale

Maybe caprover gets you close to this?