Warden uses the systemd-journal to lookup mail log information. If your logs are empty you might have a corrupted journal. You can check your journal for errors with the command:
journalctl --verifyJournald log retention options are controlled in file /etc/systemd/journald.conf. Here is a KB article about them:
https://tecadmin.net/clear-systemd-journal-logs/
The SystemMaxUse and MaxRetentionSec options control the journal data retention limits in /etc/systemd/journald.conf . If you make changes remember to restart the systemd-journal with the command systemctl restart systemd-journald .
Pruning the systemd-journal Examples
// Remove all files older than 7 days
journalctl --vacuum-time=7d
// limit the journal to 1 GB
journalctl --vacuum-size=1G
// for more help about all the options
man journalctl