DKIM (DomainKeys Identified Mail), ARC (Authenticated Receive Chain), and TLSRPT (TLS Report) email signing and verification
SPF (Sender Policy Framework) implemented in Python.
Python interface to sendmail milter API
Python SRS (Sender Rewriting Scheme) library
Python interface to libdspam
Python GOSSiP distributed domain reputation service
Anti-forgery, reputation tracking, anti-spam milter
Python DNS library