Yes, this would be greatly approved throughout the community I'm sure, I'm having tons of problems with users forwarded to Time Warner or Comcast that end up getting blocked by those providers.
This is generally why forwarding mail off of your server is a bad idea.
A better solution, and I'm not sure if Time Warner or Comcast offer this, is to set up your e-mail account at that service provider to pull e-mail from your hosting account.
I know Google Mail offers this. You can log into your gmail account and set it up to log into your POP3 server and download messages from another account and display them in your gmail account.
In this way, Google Mail is pulling mail from your cPanel based e-mail account, and your cPanel based e-mail server can never be viewed as sending spam to Google.
You may want to check and see if Time Warner or Comcast offer a similar set up.