I am experiencing the error "Error: BUG: Authentication client sent unknown handshake command:"

My goal is Port 143: no SSL; no client auth; plain password auth. Port 993: SSL; client cert auth.

I found the archive http://www.dovecot.org/list/dovecot/2016-February/103067.html

and followed it, but does not work, I see the following log in /var/log/maillog

Aug 21 15:36:42 vps0 dovecot: master: Dovecot v2.2.25 (7be1766) starting up for imap (core dumps disabled) Aug 21 15:37:51 vps0 dovecot: auth: Error: BUG: Authentication client sent unknown handshake command: REQUEST?1997012993?3734?1?e067999d43eebcecf0c9d44a1c108d75?session_pid=3741?r... Aug 21 15:37:51 vps0 dovecot: imap: Error: Authentication server didn't send valid SPID as expected: MECH#011PLAIN#011plaintext Aug 21 15:37:51 vps0 dovecot: imap: Error: Disconnected from auth server, aborting (client-pid=3734 client-id=1) Aug 21 15:37:51 vps0 dovecot: imap-login: Internal login failure (pid=3734 id=1) (internal failure, 1 successful auths): user=<contact>, method=PLAIN, rip=212.104.147.161, lip=46.30.14.36, mpid=3741, TLS, session=<UkXhtpY6W8XUaJOh> Aug 21 15:37:51 vps0 dovecot: imap-login: Disconnected (no auth attempts in 0 secs): user=<>, rip=212.104.147.161, lip=46.30.14.36, TLS handshaking: SSL_accept() failed: error:140D9115:SSL routines:SSL_GET_PREV_SESSION:session id context uninitialized, session=<nkrktpY6XMXUaJOh>

Can anyone advice any solution?

Dovecot version: 2.2.25 (7be1766) Operating system:CentOS 7, 64bit, selinux is off. CPU architecture: Intel x86 64bit. Filesystem: xfs

# /usr/local/bin/doveconf -n # 2.2.25 (7be1766): /usr/local/etc/dovecot/dovecot.conf # OS: Linux 3.10.0-327.28.2.el7.x86_64 x86_64 CentOS Linux release 7.2.1511 (Core) auth_mechanisms = plain login auth_ssl_username_from_cert = yes disable_plaintext_auth = no mail_location = maildir:~/Maildir namespace inbox { inbox = yes location = mailbox Drafts { special_use = \Drafts } mailbox Junk { special_use = \Junk } mailbox Sent { special_use = \Sent } mailbox "Sent Messages" { special_use = \Sent } mailbox Trash { special_use = \Trash } prefix = } passdb { driver = pam } protocols = imap service auth-ssl { executable = auth -o auth_ssl_require_client_cert=yes unix_listener auth-master-ssl { mode = 0666 } unix_listener login/login-ssl { mode = 0666 } } service imap-login-ssl { chroot = login executable = imap-login -l imap-ssl login-ssl inet_listener imaps { port = 993 ssl = yes } user = $default_login_user } service imap-login { inet_listener imaps { port = 0 } } service imap-ssl { executable = imap -a auth-master-ssl unix_listener login/imap-ssl { user = $default_login_user } } ssl_ca = </etc/SslCert/dovecot/2016080505CAcert.WithCrl.pem ssl_cert = </etc/SslCert/dovecot/2016080506cert.pem ssl_key = </etc/SslCert/dovecot/2016080506PrivateKey.NoPassPhrase.pem userdb { driver = passwd } protocol imap { auth_ssl_require_client_cert = no ssl_require_crl = no ssl_verify_client_cert = no } protocol imaps { auth_ssl_require_client_cert = yes ssl_require_crl = yes ssl_verify_client_cert = yes } #