Let's say a broadband ISP such as Speakeasy.net decides to publish SPF
data that says that mail claiming to be from speakeasy.net
(*(_at_)speakeasy(_dot_)net) is only authentic if it comes from mx01.speakeasy.net
or mx02.speakeasy.net. Speakeasy is a "cool" ISP that lets its
subscribers to run whatever servers/services they want to over their DSL
connection. Now lets say that Billy Bob, one of Speakeasy's subscribers
chooses to run a mail server for his vanity domain BillyBobsCrib.net
that is hosted via his DSL connection. If I understand this (and I may
not) Speakeasy's SPF record isn't in any way preventing Billy Bob from
running his MX for BillyBobsCrib.net. The only thing it prevents him
from doing is directly originating mail from speakeasy.net (without
going through Speakeasy's POP, IMAP or shell server).
Does the above sound somewhat correct?
--adam