I've a Debian mail server, but only the outlook users can't be able to download the emails.

I've seen a lot of post about some kind of forwarding port configuration, I've tried some commands, but I don't be able to solve this problem, please help me.

[LAST UPDATE] I find a lot of TIME WAIT on ipv6

netstat

tcp6       0      0 my.mailserver.it:imap2 200-62-245-188.ip2:17060 TIME_WAIT   -

below some config files:

pop3d

I think the problem was here

##NAME: POP3AUTH:1
#
# To advertise the SASL capability, per RFC 2449, uncomment the POP3AUTH
# variable:
#
# POP3AUTH="LOGIN"
#
# If you have configured the CRAM-MD5, CRAM-SHA1 or CRAM-SHA256, set POP3AUTH
# to something like this:
#
# POP3AUTH="LOGIN CRAM-MD5 CRAM-SHA1"

POP3AUTH=""

##NAME: POP3AUTH_ORIG:1
#
# For use by webadmin

POP3AUTH_ORIG="PLAIN LOGIN CRAM-MD5 CRAM-SHA1 CRAM-SHA256"

##NAME: POP3AUTH_TLS:1
#
# To also advertise SASL PLAIN if SSL is enabled, uncomment the
# POP3AUTH_TLS environment variable:
#
# POP3AUTH_TLS="LOGIN PLAIN"
POP3_TLS_REQUIRED = 0
POP3AUTH_TLS=""

##NAME: POP3AUTH_TLS_ORIG:0
#
# For use by webadmin

POP3AUTH_TLS_ORIG="LOGIN PLAIN"

##NAME: POP3_PROXY:0
#
# Enable proxying.  See README.proxy
#
# For use by webadmin

POP3AUTH_TLS_ORIG="LOGIN PLAIN"

##NAME: POP3_PROXY:0
#
# Enable proxying.  See README.proxy

POP3_PROXY=0

##NAME: PROXY_HOSTNAME:0
#
# Override value from gethostname() when checking if a proxy connection is
# required.
# PROXY_HOSTNAME=

##NAME: PORT:1
##NAME: PROXY_HOSTNAME:0
#
# Override value from gethostname() when checking if a proxy connection is
# required.

# PROXY_HOSTNAME=

##NAME: PORT:1
#
# Port to listen on for connections.  The default is port 110.
#
#  Multiple port numbers can be separated by commas.  When multiple port
#  numbers are used it is possibly to select a specific IP address for a
#  given port as "ip.port".  For example, "127.0.0.1.900,192.68.0.1.900"
#  accepts connections on port 900 on IP addresses 127.0.0.1 and 192.68.0.1
#  The ADDRESS setting is a default for ports that do not have a specified
#  IP address.
# Port to listen on for connections.  The default is port 110.
#
#  Multiple port numbers can be separated by commas.  When multiple port
#  numbers are used it is possibly to select a specific IP address for a
#  given port as "ip.port".  For example, "127.0.0.1.900,192.68.0.1.900"
#  accepts connections on port 900 on IP addresses 127.0.0.1 and 192.68.0.1
#  The ADDRESS setting is a default for ports that do not have a specified
#  IP address.

PORT=110

##NAME: ADDRESS:0
#
# IP address to listen on.  0 means all IP addresses.

ADDRESS=0

##NAME: TCPDOPTS:0
#
##NAME: ADDRESS:0
#
# IP address to listen on.  0 means all IP addresses.

ADDRESS=0

##NAME: TCPDOPTS:0
#
# Other couriertcpd(1) options.  The following defaults should be fine.
#

TCPDOPTS="-nodnslookup -noidentlookup"

##NAME: LOGGEROPTS:0
#
# courierlogger(1) options.
#
LOGGEROPTS="-name=pop3d"

##NAME: DEFDOMAIN:0
#
# Optional default domain. If the username does not contain the
# first character of DEFDOMAIN, then it is appended to the username.
# If DEFDOMAIN and DOMAINSEP are both set, then DEFDOMAIN is appended
# only if the username does not contain any character from DOMAINSEP.
# You can set different default domains based on the the interface IP
# address using the -access and -accesslocal options of couriertcpd(1).


DEFDOMAIN="@interzone.it"

##NAME: POP3DSTART:0
#
# POP3DSTART is not referenced anywhere in the standard Courier programs
# or scripts.  Rather, this is a convenient flag to be read by your system
# startup script in /etc/rc.d, like this:
#
#  . /etc/courier/pop3d
DEFDOMAIN="@mydomain.com"

##NAME: POP3DSTART:0
#
# POP3DSTART is not referenced anywhere in the standard Courier programs
# or scripts.  Rather, this is a convenient flag to be read by your system
# startup script in /etc/rc.d, like this:
#
#  . /etc/courier/pop3d
#  case x$POP3DSTART in
#  x[yY]*)
#        /usr/lib/courier/pop3d.rc start
#        ;;
#  esac
#
# The default setting is going to be NO, until Courier is shipped by default
# with enough platforms so that people get annoyed with having to flip it to
# YES every time.
#  x[yY]*)
#        /usr/lib/courier/pop3d.rc start
#        ;;
#  esac
#
# The default setting is going to be NO, until Courier is shipped by default
# with enough platforms so that people get annoyed with having to flip it to
# YES every time.

POP3DSTART=YES

##NAME: MAILDIRPATH:0
#
# MAILDIRPATH - directory name of the maildir directory.
#
MAILDIRPATH=.maildir

iptables

Chain INPUT (policy DROP 20 packets, 1016 bytes)
 pkts bytes target     prot opt in     out     source               destination         
60833   16M ACCEPT     tcp  --  eth0   *       0.0.0.0/0            0.0.0.0/0           tcp dpt:143 state NEW,ESTABLISHED 
18970  971K ACCEPT     tcp  --  *      *       0.0.0.0/0            0.0.0.0/0      tcp spts:1024:65535 dpt:110 state NEW,ESTABLISHED 


Chain FORWARD (policy DROP 0 packets, 0 bytes)
 pkts bytes target     prot opt in     out     source               destination         
    0     0 ACCEPT     tcp  --  *      *       192.168.0.0/24       0.0.0.0/0           tcp dpt:110 
    0     0 ACCEPT     all  --  *      *       0.0.0.0/0            0.0.0.0/0           state RELATED,ESTABLISHED 
    0     0 ACCEPT     tcp  --  *      *       192.168.1.0/24       0.0.0.0/0           tcp dpt:110 
    0     0 ACCEPT     all  --  *      *       0.0.0.0/0            0.0.0.0/0           state RELATED,ESTABLISHED 
    0     0 ACCEPT     tcp  --  *      *       0.0.0.0/0            0.0.0.0/0           state NEW tcp dpt:25 
    0     0 ACCEPT     tcp  --  *      *       0.0.0.0/0            0.0.0.0/0           state NEW tcp dpt:110 

pop3d.cnf

RANDFILE = /usr/lib...pop3d.rand
[req]
default_bits = 1024
encrypt_key = yes
distinguidhed_name = req_dn
x509_extensions = cert_type
prompt = no

[req_dn]
C=US
ST=NY
L= New York
O=Courier Mail Server
OU=Automatically-generated POP3 SSL key
CN=localhost
[email protected]

[cert_type]
nsCertType = server