MX records don't send messages. Assuming that “sent to them via SMTP” is meant… well, moving all messages to ‘junk’ isn't a good idea: it needs to be restricted to messages sent on or after that time. But why not just respond with “554 No SMTP service here” on opening the connection?
> From there, the email services which implement MX2 would publish a public date, on which all messages sent to them by the old MX record, will be automatically sent to Junk. If just Microsoft and Google alone agreed on such a date, that would be 40% of global email traffic.
Do you think this change wouldn't be enough? If so, why not?