mda|learn|watch: support dropUniqueUnsubscribe config

List-Unsubscribe headers with unique identifiers (such as those
generated by our examples/unsubscribe.milter) should not
end up in public archives.  Add a new config knob to strip
List-Unsubscribe headers if they have the
`List-Unsubscribe-Post: List-Unsubscribe=One-Click'
header.

Unfortunately, this breaks DKIM signatures if the signature
covers either of these List-Unsubscribe* headers.  However,
breaking DKIM is the lesser evil compared to any archive reader
being able to stop archival by an independent archivist.

As much as I would like this to be the default, it probably
affects few users at the moment since very few mailing lists
use unique identifiers in List-Unsubscribe (but that number
has grown, recently).

1 files changed, 4 insertions, 0 deletions

diff --git a/script/public-inbox-mda b/script/public-inbox-mda
index cac819ac..04fd8aad 100755
--- a/script/public-inbox-mda
+++ b/script/public-inbox-mda
@@ -16,6 +16,8 @@ use strict;
 use Getopt::Long qw(:config gnu_getopt no_ignore_case auto_abbrev);
 my ($ems, $emm, $show_help);
 my $precheck = 1;
+use PublicInbox::Import;
+local $PublicInbox::Import::DROP_UNIQUE_UNSUB; # does this need a CLI switch?
 GetOptions('precheck!' => \$precheck, 'help|h' => \$show_help) or
         do { print STDERR $help; exit 1 };
 
@@ -47,6 +49,8 @@ my $key = 'publicinboxmda.spamcheck';
 my $default = 'PublicInbox::Spamcheck::Spamc';
 my $spamc = PublicInbox::Spamcheck::get($cfg, $key, $default);
 my $dests = [];
+PublicInbox::Import::load_config($cfg, $do_exit);
+
 my $recipient = $ENV{ORIGINAL_RECIPIENT};
 if (defined $recipient) {
         my $ibx = $cfg->lookup($recipient); # first check