Notify Inactive Microsoft 365 Users via Email using Graph PowerShell

Inactive user accounts can pose a security risk or lead to unnecessary license consumption. Instead of manually tracking them, this Graph PowerShell script automatically detects inactive users and sends each of them a customized email reminder.

Perfect for IT admins looking to proactively manage user activity with automated communication.

Script – Send Notification to Inactive Microsoft 365 Users

# Connect to Microsoft Graph
Connect-MgGraph -Scopes "User.Read.All", "Reports.Read.All", "Mail.Send"
                                
# Define inactivity threshold (e.g., 90 days)
$thresholdDate = (Get-Date).AddDays(-90)
                                
# Get all users including sign-in activity
$users = Get-MgUser -All -Property Id, DisplayName, UserPrincipalName, Mail, SignInActivity
                                
# Filter inactive users
$inactiveUsers = $users | Where-Object {
    $_.SignInActivity -and $_.SignInActivity.LastSignInDateTime -lt $thresholdDate -and
    $_.Mail -ne $null
}
                                
Write-Host "`nSending custom inactivity alerts to users..." -ForegroundColor Cyan
                                
foreach ($user in $inactiveUsers) {
    $lastSignIn = $user.SignInActivity.LastSignInDateTime.ToString("yyyy-MM-dd")
                                    
    # Customize the email message
    $body = @{
        Message = @{
        Subject = "We've noticed you're inactive in Microsoft 365"
        Body = @{
            ContentType = "HTML"
            Content = @"
            Hello $($user.DisplayName),
                We noticed that you haven’t signed into your Microsoft 365 account since $lastSignIn.
                If you still need access, please sign in soon to avoid potential deactivation.
            Thank you,
            IT Administrator
            "@
            }
            ToRecipients = @(@{ EmailAddress = @{ Address = $user.Mail } })
        }
        SaveToSentItems = $true
    }

    try {
        Send-MgUserMail -UserId "admin@yourdomain.com" -BodyParameter $body
        Write-Host "Notification sent to $($user.UserPrincipalName)" -ForegroundColor Green
    }
    catch {
            Write-Host "Failed to send email to $($user.UserPrincipalName): $($_.Exception.Message)" -ForegroundColor Red
    }
}
                            

How the Script Works

1. Connects to Microsoft Graph

The script authenticates using three key delegated permissions:

• User.Read.All: To fetch user identities
• Reports.Read.All: To access sign-in activity
• Mail.Send: To send email messages via Graph
2. Defines an Inactivity Threshold

A threshold date is set (e.g., 90 days ago). Users with sign-ins before this date are considered inactive.

3. Filters and Sends Notifications

It checks each user's last sign-in and email address. If eligible, it sends a personalized HTML email using Send-MgUserMail.

4. Tracks Results in Console

Further Enhancements

You can take this automation further with the following ideas:

• Export Notified Users to CSV

Keep a log of who was notified:

$inactiveUsers | Export-Csv "NotifiedUsers.csv" -NoTypeInformation

• CC Managers

Use Get-MgUserManager -UserId to CC each user’s manager.

• Automate with Scheduler

Use Task Scheduler or Azure Automation to run the script on a weekly or monthly basis.

• Preview Mode

Add a switch to simulate sending (dry run) without actually dispatching emails.

Possible Errors & Solutions

Error	Cause	Solution
Send-MgUserMail: MailboxNotEnabled	Sender account has no mailbox	Ensure admin@yourdomain.com is a licensed user with Exchange mailbox
Access Denied or Authorization_RequestDenied	Missing Graph permissions	Use Connect-MgGraph -Scopes "User.Read.All", "Reports.Read.All", "Mail.Send"
NullReferenceException	Some users don't have SignInActivity or Mail	Filter for $_.SignInActivity -and $_.Mail -ne $null
Too many requests	Rate-limited by Graph API	Add delay (Start-Sleep -Seconds 2) between sends for large orgs

Conclusion

This script automates user communication by detecting inactive users and sending customized email reminders. It's a clean, proactive way to reduce license waste, improve engagement, and keep user directories tidy.

💡 Automation isn't just about IT efficiency—it's about making users aware, engaged, and secure.