python-libmilter started as a project to maximize the portability of libmilter. I know about, and have used, the excellent CPython implementation by Stuart D. Gathman py-milter. Though I liked this library for it's thin wrapper around the C libmilter library (and thereby speed), I had some issues with getting it to install, having to find and download the appropriate source code for libmilter version installed, etc. This is why I went with a ground up implementation of libmilter in pure Python. I want something I could just “drop in” to a project and have a milter up and running in almost no time, no matter what OS environment I was in.

I also wanted some more choices for getting things done than the default thread approach. This is why I modularized the milter itself to working as a traditional threading milter wherein each client connection gets its own thread, but I also added factories for single thread asynchronous operation and forking. Do note that the threaded version of python-libmilter is constrained by the GIL, whereas py-milter is not since the threading is implemented in C. If you really want to maximize speed, py-milter might be for you, but be aware that I've been able to get excellent performance from this library in production environments with very heavy processing load (evaluating many regular expressions) using the forking factory.

Note that this documentation assumes a good working knowledge of the SMTP protocol as defined in RFC 2822.

You will find that the library file is split up into sections defining the constants for client server options and flags. Note that there are multiple milter versions (2, 3, 4, 6) and not everything is available in earlier versions than 6. See libmilter documentation for specifics on what is available in what versions. I will show where the version 2 compatibility ends so that if you wish to write your app to be compatible with all milter versions, you can do so.

These are flags that are set defining mutations that we wish to make in our app. This first set is compatible with version 2 of the milter protocol.

This next set is available in later milter protocol versions.

There are also some convenience flags.

These are protocol options, and can be set in a couple of different ways. The first way is to simply set them when setting up your factory (TODO: link to the factory section). The other way, at least for the SMFIP_NO* and SMFIP_NR_* options, is to use decorators. That will be explained later. First, we will define the protocol options.

Again, this first section is available to version 2 of the milter protocol.

These other protocol options are defined for new versions of the milter protocol than version 2.

And just like the OPTS, there are some convenience variables for setting all protocol options.

All the rest of the standard constants are defined as well. I've only documented the ones above as these are the only ones directly used.