POP/IMAP MailBoxes

From Ezee.co.uk

This is the number of actual physical mail boxes. Each mailbox can have multiple email addresses attached to it.

For example you could have a mail box called john.smith@mydomain.com and you can add additional email addresses such as j.smith@mydomain.com or sales@mydomain.com if John Smith is responsible for sales. These three email addresses are all pointing at a single mailbox.