eMClient won't connect my email address to the server with IMAP only with POP3.I keep getting a window demanding Password & User naME

eMClient won’t connect my email address to the server using IMAP onlyPOP3.The SMTP
connects no problem.
eMClient,with IMAP,keeps asking & re-asking for Username & Password although both work
OK with POP3.
What’s happened?

This is usually because of an incorrect port and security policy combination.

Go to Menu > Tools > Accounts and make sure your IMAP settings are set to port 993, and the security policy is set to Use SSL/TLS on special port (legacy).