Problem: Ms Exchange 2000 is broken, it doesn't really expect the QUIT in ESMTP pipelinging mode before it itself said "250 Queued mail for delivery"
Result: People sending message from modern SMTP server like Postfix to Exchange 2000 server will be rejected with "500 5.3.3 Unrecognized command" , so their message cannot be delivered. I can modify my SMTP configuration so that my clients will be able to send email to Exchange 2000 server, but this dumb my software performance down a bit.
Question: Should I adjust my smtp software to consign to such broken SMTP Server ? Or let those MS admins be informed by senders themself ?