[Mimedefang] Re: Non-routable addresses in HELO

[Paul Russell]

On 11 Jul 2006, Jan-Pieter Cornet <johnpc at xs4all.nl> wrote:
 > Also note that I'm not aware of any SMTP server implementation that
 > actually enforces syntactic checks on the HELO or EHLO argument out
 > of the box (resulting in lots of clients sending utter crap). Also
 > note that blocking based on EHLO will produce some false positives:
 > there are legitimate mail servers out there that EHLO as, eg.
 > "lan.local" or something silly.

Any mail server that is so poorly administered that is not offering a properly
formatted HELO argument is not legitimate and should not be connected to the
Internet. The RFC clearly states that the server *MUST* use a FQDN or bracketed
literal IP address as the HELO argument. Anything else is explicitly prohibitted
and grounds for rejecting the connection.

-- 
Paul Russell, Senior Systems Administrator
OIT Messaging Services Team
University of Notre Dame
prussell at nd.edu