From the perspective of yours truly (and probably not anyone else), there is a relatively simple solution to this problem. I have experimented with running SMTP peer-to-peer instead of peer-to-<third_party_intermediary>-to-peer. While I first did this using L2, before Wiregaurd, Tailscale or Headscale existed,^1 I see no reason it could not be done using today's popular L3 software. One approach is the sender and recipient each run their own SMTP server on an overlay network. Each network might have its own interface, /dev/tap[0-100] being one option. Is this perfect in every way. No. Nothing meets that standard. Does it work reliably. Yes. That is good enough for me. That it works is not surprising since the early internet did not have itermediaries like Google and the early mail RFCs had no conception of third party email providers let alone "webmail", now dominated by "Gmail". Needs of "users" do differ and intermediaries might serve a useful purpose for some, even those who can make a conscious choice. Personally I have no need to be able to email every address on the planet let alone allow them to email me! More practically, I can more easily maintain smaller lists of potential senders and recipients, i.e., "networks", each one a separate network interface. Again, needs will differ based on the user.
Third party email for personal use is like using a PO Box despite have private property, a house, and an address. There is no reason that everyone cannot have their own mailbox on their own property. Even more, instead of the post office managine these PO Boxes, email uses a private entity that is trying to sell advertising services, and/or brokering direct email marketing. Both systems, snail mail and email, have been largely co-opted by the potential for direct mail marketing, so-called "junk mail". Even if one never sees any junk in their inbox (thanks to "filters"), the junk mail senders are still influencing the system. The continued enablement and presence of those junk senders, who are still sending massive quantities of junk with the help of Big Email, is why third party email providers, like Gmail, block residential IP addresses. You own property, a house and an address but you cannot have your won mailbox. That is how third party email provision works.
1. Heck, one could probably use a "lightning" network too but folks today want to use peer-to-peer overlay networks for "crypto" exclusively, not messaging or any other useful activity. Go figure. This whole means of using networks without third party intermediaries is as old as computer networks themselves. Gamers have long used LANs and overlay networks for communication, since before the internet became popular. Arguably, we could think of everything we do on the internet as a "game" that justifies use of overlays.
Third party email for personal use is like using a PO Box despite have private property, a house, and an address. There is no reason that everyone cannot have their own mailbox on their own property. Even more, instead of the post office managine these PO Boxes, email uses a private entity that is trying to sell advertising services, and/or brokering direct email marketing. Both systems, snail mail and email, have been largely co-opted by the potential for direct mail marketing, so-called "junk mail". Even if one never sees any junk in their inbox (thanks to "filters"), the junk mail senders are still influencing the system. The continued enablement and presence of those junk senders, who are still sending massive quantities of junk with the help of Big Email, is why third party email providers, like Gmail, block residential IP addresses. You own property, a house and an address but you cannot have your won mailbox. That is how third party email provision works.
1. Heck, one could probably use a "lightning" network too but folks today want to use peer-to-peer overlay networks for "crypto" exclusively, not messaging or any other useful activity. Go figure. This whole means of using networks without third party intermediaries is as old as computer networks themselves. Gamers have long used LANs and overlay networks for communication, since before the internet became popular. Arguably, we could think of everything we do on the internet as a "game" that justifies use of overlays.