This module (authres) is designed to provide support for RFC 5451/7001,
originally http://tools.ietf.org/html/rfc5451 and currently
http://tools.ietf.org/html/rfc7001, processing in Python.

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)
draft-kucherawy-dmarc-base DMARC
RFC 7281 Authentication-Results Registration for S/MIME
RFC 7293, The Require-Recipient-Valid-Since Header Field
    and SMTP Service Extension, header field types

import authres only provides the RFC 5451/7001 types. Individual additions can be
imported by name, import authres.dkim_b, authres.dkim_adsp, authres.vbr,
authres.dmarc, and authres.smime. To use all the features, the feature context
authres.all_features() is provided.

Header folding and unfolding is the responsibility of the calling application.

Between docstrings and RFC 5451/7001 the API should be reasonably clear, but the
docstrings are still a work in progress.  Additional examples are available in
the file authres/tests.  The API is completely reworked from version 0.1.

SPF authentication results can relate to either the HELO identity or the Mail
From.  When creating header fields with SPF results, only set the identity
used to evaluate the SPF result that's reported.  You can use multiple objects
to report both in a single header field.  See the example in the tests file.

This package requires python2.6 or later (including python3). It has been
tested with python2.6, python2.7, python3.2, python3.3, and python3.4.

To execute doctests, run the module as main: python -m authres

This is completely untested on Windows, but in theory should work.
