Microsoft Exchange Management Shell Commands – Get Mailbox Size Information

Exchange Management Shell has a lot of uses, and one of the most common day-to-day tasks is checking mailbox size — useful for quota management, migration planning, or tracking down what’s consuming storage.

Legacy Syntax (Exchange 2007/2010)

Get-MailboxServer "EXCHANGE-SERVER-NAME" | Get-MailboxStatistics | Select DisplayName,TotalItemSize | Sort TotalItemSize

Modern Syntax (Exchange 2013+ / Exchange Online)

Piping through Get-MailboxServer is server-specific and doesn’t translate well to newer deployments (particularly Exchange Online, where there’s no on-prem mailbox server to target). A more broadly compatible command is:

Get-Mailbox -ResultSize Unlimited | Get-MailboxStatistics | Select DisplayName,TotalItemSize,ItemCount | Sort TotalItemSize -Descending

This pulls every mailbox in the organisation (or swap Get-Mailbox for Get-Mailbox -Database "DB-NAME" to scope it to one database) and sorts largest-first, which is usually the more useful order when you’re hunting for space hogs.

Exchange Online Equivalent

If you’re connecting to Exchange Online specifically rather than a hybrid or on-prem environment, the modern EXO-prefixed cmdlets are Microsoft’s recommended, REST-backed, throttling-friendlier option:

Connect-ExchangeOnline
Get-EXOMailbox -ResultSize Unlimited | Get-EXOMailboxStatistics | Select DisplayName,TotalItemSize,ItemCount | Sort TotalItemSize -Descending

The legacy Get-Mailbox/Get-MailboxStatistics pair still works against Exchange Online too, so either approach is functional — but for larger tenants or scripted/scheduled reporting, the EXO cmdlets are the better long-term choice since they’re less likely to hit throttling limits on big result sets.

A Quicker Single-Mailbox Check

If you just need one mailbox’s size rather than the whole organisation, skip the full Get-Mailbox pipe entirely:

Get-MailboxStatistics -Identity "[email protected]" | Select DisplayName,TotalItemSize,ItemCount

Resources

• Exchange