Downgradeable encryption is arguably better than none at all. It raises an attacker's prerequisites from just passive snooping to active tampering. Yeah, it's

Downgradeable encryption is arguably better than none at all. It raises an attacker's prerequisites from just passive snooping to active tampering. Yeah, it's an illusion of security to an extent, it's imperfect, but between waiting a decade or two for SMTPS delivery to be widespread, and using STARTTLS today, I'll take STARTTLS. T̶h̶e̶y̶ ̶w̶o̶u̶l̶d̶n̶'̶t̶ ̶t̶a̶k̶e̶ ̶a̶ ̶d̶e̶l̶i̶v̶e̶r̶y̶ ̶o̶n̶ ̶p̶o̶r̶t̶ ̶2̶5̶ ̶w̶i̶t̶h̶o̶u̶t̶ ̶S̶T̶A̶R̶T̶T̶L̶S̶.̶.̶.̶ ̶i̶n̶t̶e̶r̶e̶s̶t̶i̶n̶g̶.̶ ̶ ̶D̶o̶e̶s̶ ̶a̶n̶y̶o̶n̶e̶ ̶k̶n̶o̶w̶ ̶i̶f̶ ̶t̶h̶i̶s̶ ̶i̶s̶ ̶u̶n̶i̶v̶e̶r̶s̶a̶l̶?̶ (Edit: may have spoken too soon. smtp.gmail.com responds "530 5.7.0 Must issue a STARTTLS command first." to MAIL FROM, which is I think to force a Gmail user to auth over STARTTLS before sending mail for relaying. The gmail.com MX servers don't appear to force STARTTLS.) Gmail could basically strongarm everyone into using STARTTLS and valid certs, for both sending and receiving, at which point we can release a new RFC requiring immediate STARTTLS or the connection will be closed, and everyone will already be capable of obeying it to be able to interop with Gmail.