[Dovecot] Dovecot and port forwarding

[Slawomir Wawak]

Hello!
I try to configure POP3s with Dovecot. My mail server is behind router and
I forward 995 port from router to mail server. POP3s works ok when I log
directly to 995 on server. Unfortunately, it shows nothing when I log from
outside. It happens also when the firewall is off.
All I can see in log is this:

Apr 19 13:39:43 hostname dovecot: pop3-login: Warning: SSL: where=0x10,
ret=1: before/accept initialization [123.123.123.123]
Apr 19 13:39:43 hostname dovecot: pop3-login: Warning: SSL: where=0x2001,
ret=1: before/accept initialization [123.123.123.123]
Apr 19 13:39:43 hostname dovecot: pop3-login: Warning: SSL: where=0x2002,
ret=-1: unknown state [123.123.123.123]
Apr 19 13:39:43 hostname dovecot: auth: Debug: Loading modules from
directory: /usr/lib/dovecot/modules/auth
Apr 19 13:39:43 hostname dovecot: auth: Debug: auth client connected
(pid=17056)
Apr 19 13:39:47 hostname dovecot: pop3-login: Disconnected (no auth
attempts): rip=123.123.123.123, lip=10.0.0.2, TLS handshaking: Disconnected

(hostname and IPs changed)

My config:

# 2.0.19: /etc/dovecot/dovecot.conf
# OS: Linux 3.2.0-40-generic-pae i686 Ubuntu 12.04.2 LTS
auth_debug = yes
mail_location = mbox:~/mail:INBOX=/var/mail/%u
mail_privileged_group = mail
passdb {
  driver = pam
}
protocols = pop3
service pop3-login {
  inet_listener pop3s {
    address = *
  }
}
ssl_cert = </etc/ssl/certs/dovecot.pem
ssl_key = </etc/ssl/private/dovecot.pem
userdb {
  driver = passwd
}
verbose_ssl = yes

I think it might be something related to SSL, but what?
Regards,
Slawek.