Tuta Mail, formerly Tutanota, centers privacy in its email workflow. A replacement should be tested with account recovery, search, migration, and communication with people outside the service.
Using non-sensitive test messages, send mail to another provider, receive a large attachment, search an older thread, and open the account on a second device. Check how encrypted and ordinary messages differ for recipients. Rehearse losing a device: can you recover access with the credentials or recovery material you actually keep? Export a small mailbox and verify what the new service imports, including folders, dates, and attachments.
Do not move the only copy of important messages during a trial. Record encryption assumptions and recovery limitations in plain language before changing MX records.
Akousa