Nitpickingly, while some SMTP (reicpients list) duplicated that in the email message, SMTP doesn't care about timestamps. It's the MIME stamp that can be messed

Nitpickingly, while some SMTP (reicpients list) duplicated that in the email message, SMTP doesn't care about timestamps. It's the MIME stamp that can be messed with. Most servers add a "Received" line to the MIME contents with some SMTP info, and you can't fool the timestamp inside that.