[Mimedefang] Bouncing on invalid HELO/EHLO

[Mark Frank]

On June 12, 2003, Jim McCullars wrote:
> I know there's a lot of controversy regarding bouncing mail where the
> HELO/EHLO string doesn't match the real host name, but in reading RFC1123,
> I came across this:
> 
>           Note also that the HELO argument is still required to have
>           valid <domain> syntax, since it will appear in a Received:
>           line; otherwise, a 501 error is to be sent.
> 
> How many people actually bounce mail based on this rule?

People who didn't read the 2nd paragraph above your quote.  :)


"The HELO receiver MAY verify that the HELO parameter really
corresponds to the IP address of the sender.  However, the
receiver MUST NOT refuse to accept a message, even if the 
sender's HELO command fails verification."


In practice I do filtering for a large number of customers and do a 
_lot_ of manual testing and am too lazy to type anything more than 
"helo dude" and I can't remember ever being refused.

Your quote actually refers to the _syntax_ - not the _content_ of the 
helo string.  On deciding what is a "valid <domain> syntax", a quick 
look at RFCs 1123, 952 and 921 don't really turn up anything that 
specifically say my "helo dude" is syntacially (sp?) incorrect.  I can 
be corrected though as I get cross-eyed reading RFCs.  (see my sig)

-- 
Mark Frank
"It is more complicated than you think."
   -The Eighth Networking Truth, RFC 1925