5. Select the "Encryption Method". If the upstream IMAP server uses port 143, it is likely that the encryption method is TLS and SSL for port 993. Nevertheless, you can use PLAIN authentication, but it is stongly discouraged.
Once Completed, log into the mailbox and check if all emails are imported correctly. If all goes well, All your mails shall end up in your new mailbox. And don't forget to delete or deactivate the sync job after it is used.