List all your mailbox sizes with powershell

This is one of those things that you may not use often but you are almost guaranteed to need at some point. Below is an easy powershell script/command for you to use which will export a list of all your mailboxes and their sizes, into a CSV file.

Get-MailboxStatistics | Sort-Object TotalItemSize -Descending | ft DisplayName,@{label=”TotalItemSize(MB)”;expression={$_.TotalItemSize.Value.ToMB()}},ItemCount > MailboxSizes.CSV

This is sorted by largest mailbox first and includes the name of the mailbox, the size of the mailbox (in MB) and the number of items in each mailbox.