How can I change what logwatch reports?
Copy the file you want to change from
and change the copy. This will be preserved over logwatch updates.
For example if you want to change the size of the mailbox it reports
cp /usr/share/logwatch/default.conf/services/sendmail-largeboxes.conf /etc/logwatch/conf/services
$sendmail_largeboxes_size = 400MB
No need to restart anything.