Once you get into the actual application itself ... some preparation might be necessary so that Thunderbird can see your emails properly. If you're using Gmail with Thunderbird, for example ...

Missing emails in Gmail? Check Trash, Spam, filters, and account settings to restore lost messages. Follow these steps to ...

Your email account won’t expire and your emails won’t get deleted if there are long periods of email inactivity. Automatically send a copy of incoming messages from one email account to ...