Yes. Even if we often focus on using IMAP or IMAP servers for the sake of simplicity, you can also use the POP3 protocol to access your e-mails. The host name for this protocol is pop3.mailbox.org and it is naturally encrypted using SSL. E-mail programs should detect this as part of the automatic configuration and make the necessary settings.
E-mail folders from Online Office interface do not load with POP3
E-mail folders from the mailbox.org Online-Office interface do not load with POP3. The POP3 protocol can only download e-mails from your INBOX. The (old and simple) POP3 protocol is not familiar with the concept of e-mail subfolders. E-mail folders are no problem for IMAP, but they cannot be used at all with POP3.