Quickly find Inactive Mailboxes in Exchange 2019 by using PowerShell.

Many times as Exchange Admins, we are tasked to find out if we have licenses available for new staff or we are running out of space on a server or simply just performing a cleanup and we need to know which users are inactive. In a small company this will be easier to achieve but if you dealing with thousands of mailboxes, then you need PowerShell to help you out a bit.

I have a script that searches through all the mailboxes and will display information based on what you set the Inactive date to. On line 5 of the script, you can modify the days from 90 to 30 or 60 or whichever day you require:

$inactiveDate = (Get-Date).AddDays(-90)  # In this example, 90 days of inactivity

The script has the Exchange Snapin added on line 2 incase you need to run this from another server.

Below is the output from Exchange 2019:

If you run it from PowerShell ISE, this will be the output, same as the above, just within PowerShell:

Script

Below is the script, you can save it to your Exchange server as a PS1 script file or run it from PowerShell ISE:

# Import the Exchange module
Add-PSSnapin Microsoft.Exchange.Management.PowerShell.SnapIn

# Set the date threshold for inactivity (adjust as needed)
$inactiveDate = (Get-Date).AddDays(-90)  # In this example, 90 days of inactivity

# Get all mailboxes and their statistics
$mailboxes = Get-Mailbox -ResultSize Unlimited
$inactiveMailboxes = @()

foreach ($mailbox in $mailboxes) {
    $statistics = Get-MailboxStatistics -Identity $mailbox.DistinguishedName

    # Check the last logon time
    if ($statistics.LastLogonTime -lt $inactiveDate) {
        $inactiveMailbox = [PSCustomObject]@{
            DisplayName   = $mailbox.DisplayName
            Alias         = $mailbox.Alias
            LastLogonTime = $statistics.LastLogonTime
        }
        $inactiveMailboxes += $inactiveMailbox
    }
}

# Display the results
$inactiveMailboxes | Format-Table -AutoSize

In the script I just display the information on the screen but you can modify the last line to export it to CSV if you need to.

Hope it helps.