There is a lot to like about the Omni Group's OmniFocus Mail Sync service. I've written about it before and it is amazing. Forward an email to a certain email address and a task built around that email just shows up in your inbox Omni-Synced OmniFocus database.
It gets even more interesting when you start automating email. You could, for instance, set up an Apple Mail rule that automatically forwards an email from your cable company to the the Sync Service and files the original email in your archive.
Think about that for just a moment. An email arrives, a task is created, the email gets filed. Your total involvement: zero.
You could also use something like IFTTT to do the same thing. The IFTTT hooks in Gmail give you enough control to pull it off. Create a rule that examines incoming Gmail for a particular recipient (like your cable company). Next, have Gmail forward the email to your magic Omni Sync address.
Unfortunately, this only works with Gmail. IFTTT's IMAP email account support doesn't give you enough control.
There are several local and web-based mail services that can forward an email for you. For instance, if you are working for "the man", you could set up the auto-forward in Outlook. Use a little creativity, this should work for everyone.