Find inactive mailboxes in Exchange Online

So you want to clean up unused (shared) mailboxes in your Exchange (Online) environment. How to find out which mailboxes have been inactive for a long time? The answer is yet simple again, with a cool Power Shell script.

First we will connect to Exchange Online

$Credential = Get-Credential
$Session = New-PSSession -ConfigurationName Microsoft.Exchange -ConnectionUri https://outlook.office365.com/powershell-liveid/ -Credential $Credential -Authentication Basic -AllowRedirection
Import-PSSession $Session

Now, if you want to check a single mailbox you can use the following line. By using the get-mailboxfolderstatistics command we can retrieve when the last email has been received or send.

Get-MailboxFolderStatistics obsoletemailbox@2azure.nl -IncludeOldestAndNewestItems | sort newestItemReceivedDate | where {$_.newestItemReceivedDate -ne $null} | select Identity,newestItemReceivedDate -last 1

With a few additions you can check all your mailboxes in your environment. With the get-mailbox command we will retrieve a list of all mailboxes. By looping through we should get the result for all users in a good readable format.

$mailboxes = get-mailbox

foreach ($user in $mailboxes){
Get-MailboxFolderStatistics $user.name -IncludeOldestAndNewestItems | sort newestItemReceivedDate | where {$_.newestItemReceivedDate -ne $null} | select Identity,newestItemReceivedDate -last 1

}