On Fri, Sep 09, 2005 at 02:03:10PM +0100, Tony Finch wrote:
You can try strict EHLO hostname verification if you like, but you will
find that about 1/3 of legitimate MTAs have misconfigured host names or
DNS. Widespread failure to conform to the standard is an operational
problem caused by the following text in RFC 1123:
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.
This is in rfc821, 2821 and 2821bis as well.
Also, this doesn't say anything about syntax errors (such as HELO xyyzz).
Just below what you quoted:
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.
Seems to me "HELO xyyzz" has to result in a 501 error.
Alex