Exchange Online retention and storage

Exchange Online, not on-premises Exchange

This page covers Microsoft 365 mail. See on-premises Exchange for the hosted equivalent.

Retention policies and tags

Retention controls how long mail is kept and what happens to it afterwards. Two screens work together:

• Retention policy tags define individual rules — a period and an action, such as moving to archive or deleting.
• Retention policy groups tags into a policy applied to mailboxes.

Build tags first, then assemble them into a policy.

A policy that deletes is doing exactly that

Retention runs on its own schedule against mail already in mailboxes. A delete action removes mail the user never asked to lose, without prompting, and MSPControl holds no copy.

Before applying a policy that deletes:

• Confirm the period is the customer’s actual obligation, not an assumption.
• Check what each tag does, not what it is named — a tag called “Archive 2 years” performs whatever action it was configured with.
• Apply it to one mailbox and watch a cycle before rolling it out.

Retention is usually a compliance requirement rather than housekeeping. Where a customer is subject to one, the period is theirs to state and yours to implement.

Storage usage

Reports what the tenant’s mailboxes consume, with a detail view per mailbox.

Microsoft owns this limit, not the hosting plan

Exchange Online mailbox storage is governed by the customer’s Microsoft licensing. When it runs short the remedy is with Microsoft — a licence change or additional storage — not an MSPControl quota change.

This is the opposite of on-premises Exchange, where the quota is yours to set, and it is a common source of confusion when an organization has both.

Archiving is usually the better answer than a licence upgrade for a user who genuinely needs their history: mail moved to an archive stops counting against the primary mailbox limit while staying available.

Related

• Transport and journaling rules
• Exchange Online mailboxes