The following was included in a reply to the "Odd Problem" thread, but I
wanted to get some direct feedback to my thought as expanded here.
Does it make any sense at all (or would it be appropriate) to have an
additional parameter associated with an "include:" to force MX compliance
at the included domain only if no SPF is published at the included domain
(e.g., perhaps something like "include:DNS77.COM include-:MX")?
Where the include-: could have all appropriate standard SPF syntax to
follow (e.g. IP4:, A, MX, etc).
In this way, a domain owner could be explicit about what gets sent and
received via a non-SPF publishing third party "include:" domain. For
example, if I was a LARGEISP.NET user and wanted to send mail from my
domain, but through LARGEISP.NET's MTA, if I created a record with
include:LARGEISP.NET and include-: MX, that might mean it was acceptable
for me to send mail from my domain name, through LARGEISP.NET but only via
LARGEISP.NET's MX servers.
I realize that one is essentially publishing an SPF record for another
domain in doing this, but it does allow the publishing domain name owner to
be more explicit in their desires if the include domain itself does not
publish SPF records. Perhaps a proposed "include-:" could actually use the
"all" syntax for its characters to be more clear with intent - in other
words, "include+:", "include-:", "include?:", etc.
Arguably, this could end up living longer for situations where an ISP might
not be willing or able to publish SPF records for other domains their users
might have, but might be willing to allow FROM domain through their SMTP
server for domains that publish SPF records indicating this is an
acceptable choice by the domain owner.
Perhaps another parameter might exist to let an ISP who does publish SPF to
allow or not allow that choice (e.g. a noinclude(+)(-)(?): parameter to
indicate that this behavior is not acceptable) for domain owners who might
wish such a domain owner syntax to live on past when the ISP publishes an
SPF record.
Best,
Alan Maitland
The Commerce Company - Making Commerce Simple(sm)
http://WWW.Commerco.Com/