This is a new package and I would be be happy to maintain it in Factory and
beyond. I already maintain it upstream.

Short summary: mailprocessing is a mail filter configured by user provided
Python scripts - a Turing complete mail filter if you will. It is a
fork/continuation of Joel Rosdahl's maildirproc
(http://joel.rosdahl.net/maildirproc/ ). It consists of the maildirproc utility
(which filters email in local maildirs) and the imapproc utility (which filters
email in remote IMAP folders).

In terms of packaging, maintenance overhead should be fairly low. Joel made
sure to implement maildirproc using just the Python 3 standard library and I
continued that tradition.