You are reliant on the receiver’s mail infrastructure. There have been past proposals to flip this around, such as https://en.m.wikipedia.org/wiki/Internet_Mail

You are reliant on the receiver’s mail infrastructure. There have been past proposals to flip this around, such as https://en.m.wikipedia.org/wiki/Internet_Mail_2000 https://en.m.wikipedia.org/wiki/Internet_Mail_2000