Ed uses Proton Mail, but also Gmail. Gmail tells him he has a message at Proton Mail, but he wants to get rid of Gmail. Rich says one thing to do is just log out of Gmail and it will leave him alone. Another option is to look at what third party apps have access to his Gmail account at myaccount.google.com/permissions.
Ed is tired of using Gmail. What are his alternatives? Leo says he'll want an IMAP service, and Leo uses Fast Mail. It's a pay service and it lets him use multiple devices to access the same mail in addition to a web interface. It's encrypted. Another good one is Proton Mail, which offers end-to-end encryption, if privacy is a priority.