Chuck Mead wrote:
You might want to re-examine the criteria you are using, as there
is nothing non-standard about the way our server is configured. The
EHLO our sendmailNT server uses by default is the physical server
name <SERVER3>,
This looks like a netbios name to me. It's not resolvable in any
event. It's a reality of life on today's internet that many, many
mail admins are blocking connections from hosts whose HELO does
not resolve or is not an FQDN.
I do not test for the HELO to resolve (what would be the point anyway? HELO
is too forgeable to begin with). In fact, my check is pretty lax: I just
check for a "." in the name (which covers the FQDN and address literal). The
point of the exercise is not to check whether the HELO is good, but whether
it is definitely bad.
There is only one place where I really use the HELO string (apart from SPF,
of course). And that is when I cannot get a hostname (PTR) for the
connecting host. Then I check to see whether the HELO string resolves to the
IP address of the connecting host; and, if so, consider the IP address
resolved, after all.
- Mark
System Administrator Asarian-host.org
---
"If you were supposed to understand it,
we wouldn't call it code." - FedEx