Paige is worried that she'll lose all her email someday if Google cancels her account or closes down Gmail. Leo says that FastMail is a paid service and it's a better option. However, you can back up your Gmail using Google Takeout. You could also use FastMail to go and get your Gmail if you make that choice. And you can use Evernote to back up your Gmail as well.
Derrick wants to move away from Yahoo. Leo advises going with Gmail. He can even tell Gmail to go get his Yahoo Mail to centralize it. Then he can gradually wean himself off it. FastMail is another good option.
Maggie is on Yahoo and she's thinking of moving her email account since they're going to be sold. Leo says that Gmail is a great option. It's what he uses. If she wants to pay and avoid ads and prevent a service from scanning her email for ad keywords, then FastMail is a great option. She can also set up her Yahoo mail to forward to her FastMail account, so she doesn't have to cancel it.
Cathy has a large client base and has been using Yahoo mail for her business for years. Leo says that Cathy should have her own domain (i.e. Cathy@[insertnamehere].com) and have Yahoo forward to her email service. As long as it forwards, everyone has the same email and she can change her email provider on the fly. Leo also thinks that Cathy should leave Yahoo and go with Gmail instead. Her business is too important to trust Yahoo with it. Gmail also uses IMAP, which allows her to keep copies of the email both on the server and on her PC. Forwarding is easy on GMail also.