(1) when you pay for an online service, a firm owes you a service.
(2) when you use an online service, a firm owes you nothing. Be OK with the idea that the service may disappear tomorrow.
Email is an increasingly important form of communication, and you should always have a service contract with the firm hosting your emails, with the consumer protections that come with the exchange of money for services.
I recommend fastmail.com or mailbox.org to all my family members when the topic comes up.