This may be set to C<spamc> to enable the use of SpamAssassin
L<spamc(1)> for filtering spam before it is imported into git
history. Other spam filtering backends may be supported in
-the future. This only affects L<public-inbox-watch(1)>.
+the future. This requires L<public-inbox-watch(1)>, but affects
+all configured public-inboxes in PI_CONFIG.
Default: none