Frank is having issues with Windows 10. Applications, especially Windows Live Mail, are disappearing from the task bar. Leo says that Windows Live Mail has become "depricated," with the end of life in January. Sounds like it's time to go with another mail client. Frank is with Verizon and that usually means he'd have Yahoo or Frontier mail. Leo recommends using Gmail, though. Then he can use Thunderbird by Mozilla instead of Live Mail. Or he can just use Gmail's browser client.
Once Frank signs up for Gmail, he can set it up to fetch his Yahoo Mail and sort it, so he can continue to keep Yahoo Mail active while he weans everyone off it.