This is what we do on bugs.debian.org (as of today), and it's probably a
better default even for local installations.
# user who owns /var/lib/debbugs/spool (for example, debbugs).
MAILTO=owner@bugs.example.org
*/5 * * * * /usr/lib/debbugs/spamscan >/dev/null
-3,18,33,48 * * * * /usr/lib/debbugs/processall >/dev/null
+* * * * * /usr/lib/debbugs/processall >/dev/null
7,22,37,52 * * * * /usr/lib/debbugs/rebuild db-h
9,39 * * * * /usr/lib/debbugs/html-control >/dev/null
22 7 * * * touch /var/lib/debbugs/spool/db-h