We are used to setting email accounts with the default mail quota for most of the mailboxes. However, some clients like to store a lot of emails in their accounts and we generally want to be on top of these accounts and check on how their mail account sizes and how close they are to reaching its quota. For that I created a python script that look for both size and mailbox quota and email if accounts are over certain percentage of their quotas.
We have a mirror VPS, and we hit its maximun size a few times, making our mirror unusable, and because we don't monitor it so often we missed when that happened. Here's a small script that check remove disk usage via ssh.
We also hit mirror's RAM limit, which was making rsync fail. I also added a check for a remote file timestamp and, if too old, reports that something's wrong.