Set an overall quota for Email
These days everyone is using IMAP much more, due to the increased use of phones and other devices for email. As you'd expect, people tend not to maintain their mailboxes regularly and so in many cases it is Email that takes up the majority of space in a users account. This can represent hundreds of thousands of individual files, which take a long time to backup.
It would be very useful if we could impose an overall Email quota limit in MB on a package basis. This would help force the customer to keep their mailboxes maintained.
You could argue that the package limit should determine the overall quota, but I think it is reasonable to impose terms on the customer for example that an account's email storage should be no more than, say 25% of their usage . Currently there is no way to set such a limit.