Using Xeams Community Edition Version 5.9, build 5934, on Qnap TS 453 Pro v 4.3.3.0188.  Checking for email via Thunderbird fails with "Invalid user id/password specified".

I have double-check the account and password in Xeams.   SMTP is working as there are emails in Xeams Mail Repository so the account/passord seems to be working via SMTP.

Telneting into the server and sending the user and pass commands w appropriate acct/passwd info I get "-ERR Invalid user id/password specified".

How do I get POP3 working?  Anything else I should try?