Storage usage

On-premises Exchange

This page covers hosted on-premises Exchange, not Exchange Online.

Exchange > Storage Usage reports how much storage the organization’s mailboxes are consuming, with a detail view per mailbox.

Use it to answer the two questions that actually come up: whether the organization is approaching its allocation, and which mailboxes are responsible.

Storage limits

Limits come from three places, and it is worth knowing which one is biting:

Source	Scope
Hosting plan quota	The whole organization’s Exchange storage allocation
Mailbox plan	The default limits given to a mailbox at creation
Mailbox Advanced tab	A per-mailbox override

A mailbox typically has a warning threshold, then a point at which sending stops, then a point at which delivery stops. A user reporting that they can receive but not send is usually sitting between the second and third.

Check the mailbox before raising the organization's quota

A single mailbox holding years of attachments is a more common cause of an organization approaching its allocation than genuine growth across the estate. The detail view finds it in seconds, and archiving or clearing one mailbox is cheaper than increasing the plan.

Archiving mailboxes

Where archiving is available, moving older mail into an archive takes it out of the primary mailbox’s limit while keeping it available to the user. Exchange > Archiving Mailboxes covers the archives in the organization.

This is usually the better answer than raising a limit for a user who genuinely needs their history.

Related

• Exchange mailboxes
• Mailbox plans
• Retention and ActiveSync policies

Breakdown and details

Storage Usage Breakdown splits consumption by category; Storage Usage Details opens the underlying detail.

Use the breakdown when deciding whether a space needs more quota, and the details when one mailbox is responsible for a figure that looks wrong — the two answer different questions and the breakdown alone will not identify a single offender.