spf?

[dep]

greetings, crowd . . .

time for me to undertake another breathtaking display of ignorance.

i'm on a cable modem and have used sendmail for the most part for years. 
problem is, more and more isps are blacklisting whole blocks of cable 
modem addresses.

what i'm trying to figure out is whether spf would be of any use here, 
on my machine, or whether it is something that, really, has nothing to 
do with me. i've endeavored to read what i can on the subject, but most 
of it is, like so much documentation, written in a way that suggests 
arriving at the game at about halftime.

anybody know about spf and what good it might be in a situation like 
mine? or is it something that would need to be done at the isp level?
-- 
dep

Hippocratic oath: An ethical construct whose initial tenet, "first, do 
no harm," prohibits doctors from treating lawyers.