Remove the X- prefix from some headers
Original LP Author: Barry Warsaw , LP Link: https://bugs.launchpad.net/bugs/883193
MM3 still uses a lot of X- headers, but some of the X- prefixes can be removed. In general, we can just claim the Mailman- prefix for Mailman specific headers. Candidates include:
Mailman-Rule-Hits Mailman-Rule-Misses Mailman-Version Mailman-Approved-At Mailman-LMTP-MailFrom (i.e. X-MailFrom) Mailman-Copy (or remove this header) Mailman-Content-Filter (from X-Content-Filtered-By)
Also, fix the outdated comments about add-dup-header in avoid_duplicates.py and verp.py.
Probably also get rid of X-List-Administrivia (and possibly reduced_list_headers). These seem unnecessary now.