The "Disk Quota Monitoring" is a great feature IMO, especially as more and more folks use IMAP and require ever more disk space.
There are a couple of things that would greatly improve this feature I think (unless these already exist and I'm missing them!)
1. The ability to customize the email subject line (currently "Virtualmin User Disk Quota Monitoring").
2. The ability to customize the 'from' address (or better, the "reply-to" address). This is because many users will hit "reply" in order to request support or make a comment.
Thanks for a great product.