Edit backup script

docs/content/config/troubleshooting/faq.md

@@ -25,11 +25,14 @@ You should use a [data volume container](https://medium.com/@ramangupta/why-dock
 
 Assuming that you use `docker-compose` and a data volume container named `maildata`, you can backup your user mails like this:
 
-    docker run --rm \
-    --volume dockermailserver_maildata:/var/mail \
-    -v "$(pwd)":/backups \
-    -ti tvial/docker-mailserver \
-    tar cvzf /backups/docker-mailserver-`date +%y%m%d-%H%M%S`.tgz /var/mail
+```docker run --rm -ti \
+  -v maildata:/var/mail \
+  -v mailstate:/var/mail-state \
+  -v /backup/mail:/backup \
+  alpine:3.2 \
+  tar cvzf /backup/mail-`date +%y%m%d-%H%M%S`.tgz /var/mail /var/mail-state
+
+find /backup/mail -type f -mtime +30 -exec rm -f {} \;```
 
 ### What about `mail-state` folder?
 This folder consolidates all data generated by the server itself to persist when you upgrade.