Can I also use mailbox.org with POP3

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.