# Inspired by Martin Pugh as posted here:
# http://community.spiceworks.com/topic/297650-warning-that-ad-account-will-expire
# Be sure to adjust the next 4 items between "" for your needs and check all other CAPITAL wording for replacements...
Param (
    [string]$TimeSpan = "3",
    [string]$To = "YOURSELF@YOURCOMPANY.com",
    [string]$From = "YOURServiceDesk@YOURCOMPANY.com",
    [string]$SMTPServer = "YourSMTPRelayServer"
)
Try { Import-Module ActiveDirectory -ErrorAction Stop }
Catch { Write-Host "Unable to load Active Directory module, is RSAT installed?"; Break }
# Narrowing the search down to one specific OU while ignoring one sub OU
$ExpiringUsers = Search-ADAccount -AccountExpiring -TimeSpan $TimeSpan -SearchBase "OU=USERSOU,DC=YOURCOMPANY,DC=COM" | Where-Object { $_.DistinguishedName -notlike "*OU=EXCLUDEDSUBOU,OU=USERSOU,DC=YOURCOMPANY,DC=COM*"}
# First, email administrator a list on who's expiring:
If ($ExpiringUsers)
{   $Header = @"
<style>
TABLE {border-width: 1px;border-style: solid;border-color: black;border-collapse: collapse;}
TH {border-width: 1px;padding: 3px;border-style: solid;border-color: black;background-color: #6495ED;}
TD {border-width: 1px;padding: 3px;border-style: solid;border-color: black;}
</style>
"@
    $Pre = "Accounts expiring in $TimeSpan Days"
    $Body = $ExpiringUsers | Select SamAccountName,Name,AccountExpirationDate | ConvertTo-HTML -PreContent $Pre -Head $Header | Out-String
    $SMTPSettings = @{
        To = $To
        From = $From
        Subject = $Pre
        SMTPServer = $SMTPServer
    }
    Send-MailMessage @SMTPSettings -Body $Body -BodyAsHtml
}
#Now email each user
ForEach ($User in $ExpiringUsers)
{   $ADUser = Get-ADUser $User.SamAccountName -Properties EmailAddress
    $Body = @"
Dear $($ADUser.GivenName),

Your YOURCOMPANY account $($ADUser.SamAccountName) will expire on $($User.AccountExpirationDate).
Please contact your local Human Resources Manager as soon as possible for an account extension.
 
Not responding within the given time frame results in a suspension of your account and access to your YOURCOMPANY resources will be blocked.
 
Examples being:

-         Logging into PC/Laptop.
-         Access to remote services (YOURCOMPANY Desktop/VPN).
-         Disruption of email flow on mobile devices.
 
Contact for you

-         Your local HR manager

Process

-         Our systems detect an account in the User Accounts Country Organisational Unit will expire in $TimeSpan days
-         An automatic message is sent to the employee in question
-         Employee receives email and contacts HR Manager for an account extension
-         HR Manager sends and email to the Service Desk, confirming the account extension
	-   Contains Employee name and new date of extension.
-         Service Desk informs Account Management and account is extended 

 
Your Service Desk

+1 234 5678910 Option 1 - YOURServiceDesk@YOURCOMPANY.com - HQ Office
"@
    $SMTPSettings = @{
        To = $ADUser.EmailAddress
        From = $From
	Subject = "Your account is expiring soon!"
        SMTPServer = $SMTPServer
    }
# Method 1 to send to the targeted expiring end users, if used be sure to comment (hash) the next line out and remove the hash from your second choice option:
    Send-MailMessage @SMTPSettings -Body $Body 
# Or through this way Method 2:
  # Send-Mailmessage -smtpServer $SMTPServer -from $From -to $ADUser.EmailAddress -subject "You account is expiring soon!" -body $Body -priority High
# Or for testing purposes to yourself only instead of all the end users
  # Send-Mailmessage -smtpServer $SMTPServer -from $From -to YOURSELF@YOURCOMPANY.com -subject "You account is expiring soon!" -body $Body -priority High
}