the dumbest thing is if the server refused STARTTLS or the client doesn't send STARTTLS you are supposed to still continue if you strictly follow the standard
I really hope no implementation actual does support this behavior without setting some really dangerous sounding settings (but I'm pretty sure some probably do).
at least they did standardize directly connecting with TLS by now (it not "that" long ago that while supported in practice it wasn't technically standard complaint)
> you are supposed to still continue if you strictly follow the standard
Which standard? RFC 3207 (for STARTTLS over SMTP), 2002, says: "If the client receives the 454 response [TLS not available], the client must decide whether or not to continue the SMTP session".
I really hope no implementation actual does support this behavior without setting some really dangerous sounding settings (but I'm pretty sure some probably do).
at least they did standardize directly connecting with TLS by now (it not "that" long ago that while supported in practice it wasn't technically standard complaint)