In most cases, disk space is taken up by large email boxes. It is important to identify the mailbox in question and determine the following:
- It may be that the email catch-all is not checked regularly, with email accumulating over time. Turn the catch-all off if that is the case.
- Delete mail boxes that are not being used.
- Forwarding on mailboxes to external addresses is not being cleared out. Resolve the problem by deleting the mailbox and replacing it with an alias which will forward email to the external address.