Add pflogsumm cron example

docs/u_e-postfix-pflogsumm.md

@@ -5,3 +5,12 @@ docker logs --since 24h $(docker ps -qf name=postfix-mailcow) | pflogsumm
 ```
 
 The above log output is limited to the past 24 hours.
+
+It's also possible to create a daily pflogsumm report via cron. Create the file /etc/cron.d/pflogsumm with the following content:
+
+```
+SHELL=/bin/bash
+59 23 * * * root docker logs --since 24h $(docker ps -qf name=postfix-mailcow) | /usr/sbin/pflogsumm -d today | mail -s "Postfix Report of $(date)" postmaster@example.net
+```
+
+Based on the last 24h postfix logs, this example sends every day at 23:59:00 a pflogsumm report to postmaster@example.net.