Mail::Thread is UNavailable on many distros, meaning ordinary
users will have to rely on CPAN, a Perl-specific packaging tool.
# This license differs from the rest of public-inbox
#
# Our own jwz-style threading class based on Mail::Thread from CPAN.
-# Mail::Thread is unmaintained and available on some distros.
+# Mail::Thread is unmaintained and unavailable on some distros.
# We also do not want pruning or subject grouping, since we want
# to encourage strict threading and hopefully encourage people
# to use proper In-Reply-To.