All users share domain quota without per-user quota
"See, as per iRedMail, if we want to create 50 email accounts, under a domain of 1GB quota, we can only put at most 20MB as the disk quota for each email account. Am I right? Also if we need to create additional email accounts over this, we have to play with the quota again and that will be a big headache. It would be nice if each email accounts share the available disk space in the domain until the domain quota gets full (like cPanel)."