If you are unable to login to your email accounts and the system shows this error message:

Plaintext authentication disallowed on non-secure (SSL/TLS) connections

If you don’t want to use SSL/TLS connection to get your email, and to disable SSL/TLS secure connection.

You can verify this error using telnet as follows.

[ryan@ ~]$ telnet mail.domain.com 110
Trying 192.40.112.75…
Connected to mail.domain.com.
Escape character is ‘^]’.
+OK Dovecot ready.
user ryan@domain.com
-ERR [AUTH] Plaintext authentication disallowed on non-secure (SSL/TLS) connections.

>> Edit dovecot configuration file: /etc/dovecot.conf

>> Change the value for this directive from:

disable_plaintext_auth = yes
TO:
disable_plaintext_auth = no

Restart service dovecot and exim
# /etc/init.d/dovecot restart
# /etc/init.d/exim restart

If these steps are not working check cPanel logs.

Error :-
PHP Fatal error: Call to undefined function logout_error() in /usr/local/cpanel/base/3rdparty/squirrelmail/plugins/login_auth/functions.php on line 282

Check the file permission

# ls -l /usr/local/cpanel/bin/dovecot-wrap
-rwsr-x— 1 root dovecot 9176 Apr 9 2013 /usr/local/cpanel/bin/dovecot-wrap*

chmod +x dovecot-wrap

In my case the issue was unresolved, so I ran an upcp that fixed the issue.

[ryan@ ~]$ telnet mail.domain.com 110
Trying 192.40.112.75…
Connected to mail.domain.com
Escape character is ‘^]’.
+OK Dovecot ready.
user ryan@domain.com
+OK
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