SMTP send mail to users

HI,

I found this PowerShell on internet, when I run the PowerShell script I get the following error.  All my users are on a domain. do I need to pass something into the powershell?


send-mailmessage : The SMTP server requires a secure connection or the client was not authenticated. The server response was: 5.7.1 Client was not authenticated
At line:38 char:1
+ send-mailmessage -to $email -from noreply@domain.org -Subject "Password Reminder: ...
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : InvalidOperation: (System.Net.Mail.SmtpClient:SmtpClient) [Send-MailMessage], SmtpException
    + FullyQualifiedErrorId : SmtpException,Microsoft.PowerShell.Commands.SendMailMessage


import-module ActiveDirectory;
$maxPasswordAgeTimeSpan = (Get-ADDefaultDomainPasswordPolicy).MaxPasswordAge
Get-ADUser -filter * -properties PasswordLastSet, PasswordExpired, PasswordNeverExpires, EmailAddress, GivenName | foreach {
    $today=get-date
    $UserName=$_.GivenName
    $Email=$_.EmailAddress
   if (!$_.PasswordExpired -and !$_.PasswordNeverExpires) {
        $ExpiryDate=$_.PasswordLastSet + $maxPasswordAgeTimeSpan
        $DaysLeft=($ExpiryDate-$today).days
        if ($DaysLeft -lt 5 -and $DaysLeft -gt 0){
        $WarnMsg = "
<p style='font-family:calibri'>Hi $UserName,</p>
<p style='font-family:calibri'>Your Windows login password will expire in 5 days, please press CTRL-ALT-DEL and change your password.  As a reminder, you will have to enter your new password into your DOMAIN connected mobile device if prompted.</p>
<p style='font-family:calibri'>Requirements for the password are as follows:</p>
<ul style='font-family:calibri'>
<li>Must not contain the user's account name or parts of the user's full name that exceed two consecutive characters</li>
<li>Must not be one of your last 7 passwords</li>
<li>Contain characters from three of the following four categories:</li>
<li>English uppercase characters (A through Z)</li>
<li>English lowercase characters (a through z)</li>
<li>Base 10 digits (0 through 9)</li>
<li>Non-alphabetic characters (for example, !, $, #, %)</li>
</ul>
<p style='font-family:calibri'>For any assistance, visit the <a href='http://ITHelpDesk'>IT Help Desk</a></p>
<p style='font-family:calibri'>-Technology Services</p>
"
ForEach ($email in $_.EmailAddress) {
send-mailmessage -to $email -from noreply@domain.org -Subject "Password Reminder: Your password will expire in $DaysLeft days" -body $WarnMsg  -smtpserver smtpserverIP -BodyAsHtml }

Write-Host "$email"
         }
    }
}