--On 14 January 2010 14:52:40 -0600 Don Lee
<spfdiscuss(_at_)caution(_dot_)icompute(_dot_)com> wrote:
On the one hand, CNAME for HELO is all too common (and accepted - wrong
though it may be), but HELO that does not resolve, or does not have
port 25 open on the resolved IP is more and more commonly the reason
for mail from that server being rejected.
There's no reason that my sending mail server should have port 25 open. Many
sites separate their outbound and inbound servers. Sender verifications rely
on MX records, which could point anywhere.
Quite right, but that's not my point.
My point is that legit mailservers have substantial incentive to
use something reasonable for HELO. Random junk for HELO _will_ cause
e-mail delivery problems to various servers that require one or
more of the "non-required" HELO tests.
For instance, there are servers out there that only accept mail if
HELO resolves to a server with port 25 open AND accepts mail to the
MFROM address.
That's not kosher, but it's not that uncommon (esp in Europe)
If they can get away with all those hoops, then I can require that the
HELO at least resolve.
Bottom line - I do not hesitate to require reasonable HELO values,
because unreasonable ones from legit servers are so very rare.
-dgl-
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