RFC 5451/7001/7601 Authentication- Results Headers generation and parsing for Python/Python3.

It also supports Authentication Results extensions:

RFC 5617 DKIM/ADSP
RFC 6008 DKIM signature identification (header.b)
RFC 6212 Vouch By Reference (VBR)
RFC 6577 Sender Policy Framework (SPF)
RFC 7281 Authentication- Results Registration for S/MIME
RFC 7293 The Require- Recipient- Valid-Since Header Field
RFC 7489 Domain-based Message Authentication, Reporting, and Conformance (DMARC)
Authenticated Recieved Chain (ARC) (draft- ietf-dmarc- arc-protocol- 08)

Note: RFC 7601 obsoletes RFC 5451, 6577, 7001, and 7410. Authres supports the current standard. No backward compatibility issues have been noted.