System.Net.Mail being redirected to other addresses

Problem: 
I have a small aspx site setup that uses System.Net.Mail on a few pages to send mail using Godaddy's relay-hosting.secureserver.net.  The site is hosted there as well.   The site will send me an email when someone logs in, visits certain pages, or when a client updates their information.  All of these emails are set to be From my address and To my address and it works fine.  What's happening however is about once a day, I'll get a mailer-daemon message saying that  the mail message  was not deliverable to about 15-20 addresses.  The content of the message is exactly like I would expect from my site, so it's not been changed for spamming.   I don't recognize any address nor are any of these addresses in the database the site uses nor are they anywhere in the directory of the site.

Solution:
 The answer is to use an alternative  for relay-hosting.secureserver.net.
The email server don't support that the email have too much email address.
You can try another email server to test it.