This quick, easy to follow guide will help you to export a CSV file listing all of the mail items within their respective folders and sub-folders. This script will work on both Exchange and O365.
To get started in O365, you’ll need to open a remote powershell session:
$Session = New-PSSession -ConfigurationName Microsoft.Exchange -ConnectionUri https://ps.outlook.com/powershell/ -Credential $o365cred -Authentication Basic -AllowRedirection
Then run this script to export to a file:
get-mailboxfolderstatistics -identity firstname.lastname@example.org | select FolderPath, FolderSize, ItemsinFolder, ItemsInFolderandSubfolders | Export-csv example.csv
That’s it, you’re done!