One of those well known providers

> (Spamming via SRS has not actually happened to me. I am just taking the
> original posters complaint seriously. It is entirely possible
> that the "well known provider" forwarding him all the spam via SRS
> is legitimately doing so because he himself asked them to - which
> is not a good idea if you check SPF and the forwarder does not.)

Trust me that day will come where it hits you too....

To give the "well known provider" a name:

Schlund & Partner - one of Europes biggest webhoster (also known as
kundenserver.de):

https://service.schlund.de/service/news/news_neu.php3

" 28.02.2005 -  SRS  auf den Mailservern aktiv 
Auf den Mailservern wurde das Sender Rewriting Scheme (kurz SRS) aktiv
geschaltet, um Zustellprobleme im Zusammenhang mit SPF (Sender Permission
Framework) zu vermeiden. SPF wird auf unseren Mailservern derzeit nicht
eingesetzt, ....."
Translation:
28.02.2005 - SRS acivated on the mailservers
At the Mailservers Sender Rewriting Scheme (short SRS) was activated, in
order to avoid delivery problems in conjunction with SPF (Sender Permission
Framework). SPF is actually not used on our Mailservers ...."
I don´t want to know, if such big companys doing such things, how many
little ISPs will follow their bad example ...
-- 

Johann Steigenberger 
Blacklistmaster at UCEPROTECT-Network 
http://www.uceprotect.net