I always expect to find weird SMTP status codes… After all i dont trust Exchange MTA anymore since the greylisting bug….
But it is always amusing to find something like this (used by qmail)
25 - - 354+go+ahead+punk,+make+my+day with reference to http://pobox.com/~djb/docs/smtplf.html
This was actually caused by bad formatting with a non RFC 821 compliant SMTP client…
If you keep in mind that this error code message may appear in NDR to a user – which may potenially be a customer – this method is not really suited to handle noncompliance.