Why are my email messages being moved into the Trash folder?

Question

Why are my email messages being moved into the Trash folder?

Answer

If your email account is configured on an email client that uses the POP3 protocol, and that client is set up to both delete messages after it has downloaded them from the server and to delete the messages permanently after a certain number of days, the client will move the messages into the Trash folder after it has downloaded them. To make sure your messages are not deleted, you should either disable the settings or configure the email client to use the IMAP protocol instead, which only downloads the message headers and does not remove any messages in the process of checking mail.