String is not in the form required for a subject?

I was trying to hash a few various scripts together into one powershell script and have it email some output to me when it completed.  I would then schedule the script to do a daily report.  All seemed to work fine until I added the email code part.  My code was like:

$emailFrom = "user@yourdomain.com"
$emailTo = "user@yourdomain.com"
$subject = "your subject"
$body = "your body"
$smtpServer = "your smtp server"
$smtp = new-object Net.Mail.SmtpClient($smtpServer)
$smtp.Send($emailFrom, $emailTo, $subject, $body)

When I added it and ran the script I received an error like:

System.Net.Mail: The specified string is not in the form required for a subject

Googling around did not yield an obvious answer.  I kept digging and found reference to line feeds or odd characters in the subject and I made sure that was not the case.   Eventually I found a post mentioning the LENGTH of the subject line.  Apparently there is some character limit.  As soon as I cut my subject line down to just several words instead of a longer more verbose output, it worked.