All Mailboxes

The question it answers: Which mailboxes exist in Exchange Online, of which type, and how large are they?

Note

Sizes are the byte counts from Get-MailboxStatistics (TotalItemSize), one call per mailbox, so large tenants take a while; a mailbox whose statistics cannot be read shows 0. Discovery search mailboxes are left out.

At a glance

Where in the app	Exchange Online › Mailboxes › All
Workload	Exchange Online
Kind	Table
Data	Read from Microsoft 365 when someone first opens it, then kept for the report cache lifetime (Settings > Data & cache, 1 hour unless changed). It reads through PowerShell (Exchange Online or SharePoint Online), so the first load takes longer than a Graph report.
Licence	Exchange Online.
Report id (API and MCP)	exchange.mailboxes.all

Columns

Column	Key	Type
Display Name	DisplayName	Text
User Principal Name	UserPrincipalName	Text
Primary Address	PrimarySmtpAddress	Text
Mailbox Type	RecipientTypeDetails	Text
Mailbox Size (GB)	StorageUsedGB	Text

What it needs

Licence: Exchange Online.

Application permissions on the IntensiveReports app registration (all permissions):

Permission	API	What it allows	Note
Exchange.ManageAsApp	Office 365 Exchange Online	Manage Exchange As Application	+ View-Only Recipients

Data sources it reads

• PowerShell: Get-ExoMailbox -ResultSize Unlimited
• PowerShell: Get-MailboxStatistics (per mailbox)

Through the API and MCP

GET /ir-api/v1/reports/exchange.mailboxes.all?size=100

An AI assistant reads it with the MCP tool get_report and the id exchange.mailboxes.all. The client needs the Read grant for Exchange Online. See Using the API.