Python SRS (Sender Rewriting Scheme) library
Python SRS (Sender Rewriting Scheme) library. As SPF is implemented, many MTAs that check SPF must account for forwarders. One way to handle forwarding is to rewrite envfrom to a domain that is authorized for the forwarding MTA.
See http://www.openspf.org/SRS for details.
The Perl reference implementation is at http://www.anarres.org/projects/srs/