User login activity

@TonicXsonic

$Event = Get-WinEvent -LogName 'Security' -MaxEvents 1 -FilterXPath "*[System[EventID=4624]]"
$EventXML = [xml]$Event.ToXml()
$Username = ($EventXML.Event.EventData.Data | Where-Object {$_.Name -eq 'TargetUserName'} | Select-Object -Property '#text')."#text"

if ($Username -ne 'ANONYMOUS LOGON') {
Send-MailMessage -To "your_email@example.com" -From "alert@example.com" -Subject "New User Login" -Body "User $Username has just logged in." -SmtpServer "smtp.example.com"
}

Task Scheduler Method with Event Trigger

1. Open Task Scheduler and create a new task.
2. Set the Trigger to "On an event" and configure it to monitor the Security log for Event ID 4624.
3. Set the Action to "Send an email" and fill in the necessary email information.
4. Finish the setup to activate the task.

Note: Starting with Windows Server 2012 and Windows 8, sending email via Task Scheduler is deprecated, so you may want to have the task run a PowerShell script to send the email, like in the PowerShell method above.