Other things to consider before SRSing:
1. Could you bounce the message back to the sender anyway
(is the sender addres valid; is there a MX waiting for the bounce)?
2. Does the SPF record end with the +all directive (rendering it useless)?
These two techniques are sometimes used by spammers, particularly
the "tworandomwords.com" brigade.
--
Regards,
Martin Nicholas.
E-mail: reply-2010@???