I have two additional questions that this message has triggered:
1) Why aren't Disposition-Notification-To headers removed?
2) Why doesn't jeeves.archives.listbox.com have an SPF record?
Harvey Coward wrote:
My email SMTP server is hosted externally.
I have been advised by the openspf.org wizard that the MTA should have
an SPF record.
That serves a twofold purpose: protecting the corresponding email
addresses, and having a valid helo name for bounces (or any message
sent without a MAILFROM.)
I have asked the service provider to publish an SPF record but they
reply that:-
QUOTE
[...]
As no mail is generated as being FROM mail4.ukisp.com, the requirement
for an SPF record is neglible. Backscatter in this instance is not a
problem as no valid recipients at mail4.ukisp.com will exist, therefore
be accepted.
UNQUOTE
That addresses the protection purpose.
My question - are they correct?
Yes, in part. They should also state that no bounces (or any message
without a MAILFROM) are ever sent from that host. I think they have
turned out backscatter for any message that will result to be
undeliverable after having been accepted by mail4.ukisp.com from
external sources, but it may be a good idea to ask for more details.
As a marginal case, a check could be missed from internal sources.
What happens to undeliverable messages that you send? If you write to
unexisting-user(_at_)existing-domain, your message may make its way to
mail4 and only there be found to be undeliverable. In that case, a
bounce would be generated with a helo name that misses an SPF record,
thereby producing an output of "none" if the internal receiver runs
SPF checking against its MX, or your client might discard it on a
similar basis.
If they are correct, why is there not more accurate guidance at
openspf.org?
That point has never been accurately worked out. The FAQs barely
mention it in http://www.openspf.org/FAQ/The_demon_question
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