Verisign changes violates RFC2821

[Avleen Vig <lists-nanog () silverwraith com>]

Just to make it clear, RFC2821 is likely being violated:
   -  The reserved mailbox name "postmaster" may be used in a RCPT
      command without domain qualification (see section 4.1.1.3) and
      MUST be accepted if so used.

This is *probably* being violated, but I'm not sure as it gets ambiguous
later.

However, returning a 550 is very wrong. The correct reply should be
either:
    554 Transaction failed (Or, in the case of a connection-opening
    response, "No SMTP service here")
or:
    502 Command not implemented