SMTP "forwarding" (sending an email message with a header "To: <originaladdress>", to a different "RCPT TO: <differentaddress>") is "broken by design"? Sure, i

SMTP "forwarding" (sending an email message with a header "To: <originaladdress>", to a different "RCPT TO: <differentaddress>") is "broken by design"? Sure, it's probably silly. But, SMTP is what it is, and you're not going to change it by complaining SPF's design just ... forgot about this, which happens all the time for email. Every MTA -- literally every forwarding MTA -- does this all day long, and every receiving MTA (which looks at the "Return-Path: <originaladdress>" to lookup the SPF TXT record), gets your fancy "v=spf1 ... nothing w/ forwarding MTA in it ... -all" record, and summarily executes the email w/ SPF: FAIL? It's just wrong. SPF can only serve as one (strong) hint that an email might be correct, if it passes. If it fails, all your MTA can assume is: "well, the email was very likely forwarded"; what else does it have going for it? If its "DKIM-Signature: ..." header is valid, that it's almost certainly A-OK! So, why do you want all your domain's nicely DKIM-signed emails dropped, just because some recipient decided to use a "forwarding" email address? That seems silly.