''Q1) Where does Thunderbird for Android save POP3 Mailboxes?'' The mailbox data is stored within protected internal storage (app sandbox). It's not accessible unless you have a rooted phone. ''Q2) Is there a Backup-Restore Feature for POP3 Mailboxes?'' Thunderbird for Android doesn't currently offer any backup or restore mechanism for mailbox data. You can add your idea(s) on Mozilla connect and receive votes from the community. The TB team take these into consideration when planning feature additions and roadmaps. https://connect.mozilla.org/t5/ideas/idb-p/ideas/label-name/thunderbird%20android

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