Some emails sent from our SMTP Server (Windows 2008 running IIS6 SMTP) have begun failing with some of the following errors:
Action: failed Status: 5.5.2 Diagnostic-Code: smtp;504 5.5.2 <178867-WWW1>: Helo command rejected: need fully-qualified hostname
Action: failed Status: 5.5.0 Diagnostic-Code: smtp;550 Access denied - Invalid HELO name (See RFC2821 4.1.1.1)