You must check that the port for (POP or IMAP) is the correct port.
Mine is 993 for IMAP and 995 for POP and also the mail box protocol (mine is IMAP+SSL)
Keep in mind some servers require the complete email address as an username some others only the whatever@ before the @ sign.

Also at the SMTP i have added to my host name
tlsv1.2://mail.hostname.xxx
as this was the only way i could send a reply.
Authentication is required also.

Try to review these settings.