For consumers, ignoring a SHOULD mostly affects their own robustness.
But here Google seems to understand it as a MUST... maybe the scale of spam is enough to justify it. Users are stuck between two parties that expect the other to behave.
This is 100 percent the case, and why these things are this way.
If you wanted to make email two point oh, I dont think it would look a lot like what we have today.
> If you wanted to make email two point oh, I dont think it would look a lot like what we have today.
Would this make mass emails and spam harder, absolutely. Would it be a huge burden for actual communications with people, not so much. From there actual white/black listing processes would work all that much better.
It would simply close the loop and push the burden of the messages onto the sender's system mostly.
And yes, you can decide from the envelope, and a higher chance of envelope validity.
But gmail accepts emails without message-id on personal mailboxes apparently.