Vista - How do I pass credentials for email to be sent through Exchange 2003

I have the following code that I would like to use for emailing an
alert out. I am working on a script that will run checking a series of
directories for files older than 2 days currently. This is for our
dictation users. If there are files older than 2 days, they
potentially will have issues with Transcription in the next couple of
weeks after that. I am trying to be pro-active and find these
potential issue earlier than later.

I have ran this and I get that I am not allowed to send email through
our exchange box. Which is good, but now I can't figure out how to
pass login info through so that I can send the email.

TIA for any help.

Tim


# emailing results
$SmtpServer = "server.domain.local"
$From = "timparker@xxxxxx"
$To = "timparker@xxxxxx"
$subject = "Potential Dictation Issue"
$smtp = new-object system.net.mail.smtpClient($SmtpServer)
$mail = new-object System.Net.Mail.MailMessage
$mail.From = $From
$mail.To.Add($To)
$mail.Subject = $subject
$mail.Body = "There is a problem, send out the Transcription Police.
"
$mail.IsBodyHtml = $false
$smtp.Send($mail)