WIP: Add support for new SpamAssassin subjprefix keyword
Starting with the upcoming SpamAssassin 3.4.3 release a new subjprefix will be introduced. It will be possible to add a Subject prefix to email's Subject based on specific rules. A little patch is needed to support this feature in Amavis.
A tipical SpamAssassin rule to test this feature is:
if can(Mail::SpamAssassin::Conf::feature_subjprefix)
enlist_addrlist (GITLABEMAIL) *@gitlab.com
header GITLAB eval:check_from_in_list('GITLABEMAIL')
describe GITLAB Gitlab emails
score GITLAB 0.001
subjprefix GITLAB [Gitlab]
endif