[Mimedefang] Bouncing on invalid HELO/EHLO

[David F. Skoll]

On Thu, 12 Jun 2003, Mark Frank wrote:

> "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."

That's ambiguous.  Does it mean you can't reject a message if the HELO
parameter fails that single test (IP address doesn't match), or you
can't reject if the HELO parameter fails any other test of your
choosing?

> 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.

RFC 2821:

2.3.5 Domain

   A domain (or domain name) consists of one or more dot-separated
   components.  These components ("labels" in DNS terminology [22]) are
   restricted for SMTP purposes to consist of a sequence of letters,
   digits, and hyphens drawn from the ASCII character set.

--
David.