Your mailbox is an area of storage on one of the ISS mail servers, which is assigned to your login name. The mail system delivers all email addressed to you to this location.
Your mailstore is the amount of disk storage assigned to your mailbox. Mailstore is assigned in fixed, default amounts: see details on mail quotas.
Almost all members of the University have their mail delivered to the Outlook Exchange service. Staff and PhD students use 'full' Outlook Exchange on their office PCs; all taught students use Outlook Web Access (OWA) only. The Exchange service comprises many interlinked computers and servers.
In the past, any member of staff or PhD student, could request that their mailbox be allocated on a Unix server called Cyrus. Please note that this service is no longer available to new users.