Dovecot POP3 STARTTLS works on Thunderbird but not on Gmail

[Aleš Grm]

Hello,

I have configured Dovecot to work perfectly on Thundrebird using SSL
certificates with STARTTLS on port 110. When I try to add this account on
Gmail I get the error:

Nov 16 14:04:17 mail dovecot: auth: Debug: auth client connected (pid=31587)
Nov 16 14:04:17 mail dovecot: pop3-login: Disconnected (no auth attempts in
0 secs): user=<>, rip=209.85.160.136, lip=192.168.100.94,
session=<gxLlf/kHwgDRVaCI>


In Gmail my settings include port 110 and the use of SSL is checked.
Dovecot configuration:

# 2.1.7: /etc/dovecot/dovecot.conf
# OS: Linux 3.2.0-4-amd64 x86_64 Debian 7.7
auth_debug = yes
auth_debug_passwords = yes
auth_mechanisms = plain login
auth_verbose = yes
auth_verbose_passwords = plain
disable_plaintext_auth = no
hostname = kopitarna.eu
mail_debug = yes
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
}
postmaster_address = postmaster at kopitarna.eu
protocols = " imap pop3"
ssl_cert = </etc/ssl/certs/www.kopitarna.com.crt
ssl_key = </etc/ssl/private/www.kopitarna.com.key
userdb {
  driver = passwd
}
verbose_ssl = yes

Any idea why does it work with Thunderbird and not with Gmail?