Devecot cannot perform authentication

Devecot cannot perform authentication-Linux Enterprise Application-Linux server application information. The following is a detailed description. Devecot cannot perform identity authentication. telnet is used for testing:

[Root @ localhost ~] # Telnet 127.0.0.1 110
Trying 127.0.0.1...
Connected to localhost. localdomain (127.0.0.1 ).
Escape character is '^]'.
+ OK Dovecot ready.
User admin@cc.com
+ OK
Pass 111111
-ERR Authentication failed.

Obviously, the email client cannot send and receive emails normally at this time. The message is as follows:
An error occurred while logging on to the email server. The "password" is rejected. Account: '192. 168.2.6 ', server: '192. 168.2.6', protocol:
POP3: Server Response: '-ERR Authentication failed.', Port: 110, security (SSL): No, server error: 0x800CCC90, error code: 0x800CCC92

Dovceot is properly installed and port 110,143 is enabled, but authentication cannot be performed. Please advise. Answers are urgently needed. Thank you.