Hi all,
after reconfiguring /etc/courier-imap/pop3d-ssl in this way:
SSLPORT=995
SSLADDRESS=0
SSLPIDFILE=/var/run/pop3d-ssl.pid
SSLLOGGEROPTS="-name=pop3d-ssl"
POP3DSSLSTART=NO
POP3_STARTTLS=YES
POP3_TLS_REQUIRED=1
COURIERTLS=/usr/bin/couriertls
TLS_PROTOCOL=TLS1
TLS_STARTTLS_PROTOCOL=TLS1...