I would never run a mail server without a reverse DNS to check the pointer record. If the yourdomain.com reverse lookup comes back as something else, my server would drop your connection like a ton of bricks. That is the first line of defense, even before spamhaus and black lists were event a thought. Hey I remember sending an Email to a buddy from whitehouse.gov at one time. Now that was funny and could land you in jail. But it only went to him. If a mail server does not do a reverse lookup at the pointer record, who's to say where the mail came from. I could call my server anything. So yes Verizon must manage the pointer records for their static IPs, and should for a business customer. Perhaps you need to call the old MCI people to get someone that knows something.
