What happens if I select the "Allow POP3 access to emails older than POP3 access activation" checkbox?
If you select this checkbox in the "POP3 access" section in the "Settings" tab, you will be able to download emails that were received before POP3 access activation.
If you select the "Allow POP3 access to emails in 'Sent mail' folder" and the "Allow POP3 access to emails older than POP3 access activation" checkboxes, you will be able to download messages that were sent and received into the Spam folder before you activated POP3 access.