This is a DKIM signing and verification milter. In theory it has been tested
with both Postfix and Sendmail.

The configuration file is designed to be compatible with OpenDKIM, but only
a subset of OpenDKIM options are supported. If an unsupported option is
specified, an error will be raised.

This package includes a default configuration file and man pages. For those
to be installed when installing using setup.py, the following incantation is
required because setuptools developers decided not being able to do this by
default is a feature:

python3 setup.py install --single-version-externally-managed --record=/dev/null

For users of Debian Stable (Debian 9, Codename Squueze), all dependencies are
available in either the main or backports repositories:

[sudo] apt install python3-milter python3-nacl python3-dnspython
[sudo] apt install -t stretch-backports python3-authres python3-dkim

The preferred method of installation is from PyPi using pip (if distribution
packages are not available):

[sudo] pip3 install dkimpy_milter

Using pip will cause required packages to be installed via easy_install if they
have not been previously installed. Because pymilter and PyNaCl are compiled
Python extensions, the system will need appropriate development packages and
an C compiler. Alternately, install these dependencies from distribution/OS
packages and then pip install dkimpy_milter.

The milter will work with either py3dns (DNS) or dnspython (dns), preferring
dnspython is both are available. The dkimpy DKIM module also works with
either.

Both a systemd unit file and a sysv init file are provided. Both make
assumptions about defaults being used, e.g. if a non-standard pidfile name is
used, they will need to be updated. The sysv init file is Debian specific and
untested, since the developers are not using sysv init. Feedback/patches
welcome.

The dkimpy-milter drops priviledges after setup to the user/group specified in
UserID. During initial setup, this system user needs to be manually created.
As an example, using the default dkimpy-user on Debian, the command would be:

[sudo] adduser --system --no-create-home --quiet --disabled-password \
               --disabled-login --shell /bin/false --group \
               --home /run/dkimpy-milter dkimpy-milter

Since /var/run or /run is sometimes on a tempfs, if the PID file directory is
missing, the milter will create it on startup.

As with all milters, dkimpy-milter needs to be integrated with your MTA of
choice (Sendmail or Postfix).

The python DKIM library, dkimpy, requires the entire message being signed or
verified to be in memory, so dkimpy-milter does not write messages out to a
temp file. This may impact performance on low-memory systems.

This is an initial production release to support interoperability testing with
Ed25519 signatures sufficient functionality for basic use. The documented
functionality has been implemented and at generally partially tested. It is
free of known defects, but is not fully tested in a variety of environments.

DKIM Ed25519 signatures are described in RFC 8463.

See the package README for additional details.