Buenas.
Monte un CentOS 6 e instale Postfix+Dovecot+Saslauth, he abierto los puertos tanto para conectar a los buzones como para el envio de correos, aqui un escaneo de como luce desde afuera:
21/tcp open ftp 22/tcp open ssh 53/tcp open domain 80/tcp open http 110/tcp open pop3 143/tcp open imap 993/tcp open imaps 995/tcp open pop3s 8080/tcp open http-proxy
Tengo muchos abiertos porque mi servidor funje como router tambien, para la red interna mi servidor es un ProxyWeb, FTP, DNSMasq (dhcp), HTTP (uso Virtuales) y Correos.
El puerto 25/smtp aparece como *filtrado*.
Regla que uso para el 25 en iptables: *iptables -A INPUT -i eth0 -p tcp --dport 25 -j ACCEPT #smtp*
Cuando envio un correo recojo esto en el log:
May 9 19:48:52 server postfix/pickup[24744]: 4AB933EE1: uid=48 from=< contacto@crver.net> May 9 19:48:52 server postfix/cleanup[24855]: 4AB933EE1: message-id=< 20130510004852.4AB933EE1@server.crver.net> May 9 19:48:52 server postfix/qmgr[24745]: 4AB933EE1: from=< contacto@crver.net>, size=804, nrcpt=1 (queue active) May 9 19:49:22 server postfix/smtp[24857]: connect to gmail-smtp-in.l.google.com[173.194.77.26]:25: Connection timed out May 9 19:49:52 server postfix/smtp[24857]: connect to alt1.gmail-smtp-in.l.google.com[74.125.130.26]:25: Connection timed out May 9 19:50:22 server postfix/smtp[24857]: connect to alt2.gmail-smtp-in.l.google.com[173.194.74.26]:25: Connection timed out May 9 19:50:52 server postfix/smtp[24857]: connect to alt3.gmail-smtp-in.l.google.com[173.194.73.26]:25: Connection timed out May 9 19:51:22 server postfix/smtp[24857]: connect to alt4.gmail-smtp-in.l.google.com[173.194.67.26]:25: Connection timed out May 9 19:51:23 server postfix/smtp[24857]: 4AB933EE1: to=< darkdiabliyo@gmail.com>, relay=none, delay=151, delays=0.13/0.07/151/0, dsn=4.4.1, status=deferred (connect to alt4.gmail-smtp-in.l.google.com[173.194.67.26]:25: Connection timed out)
No se si me falte configurar algo mas en el postfix, nose... le dejo mi configuracion:
*shell# postconf -n* alias_database = hash:/etc/aliases alias_maps = hash:/etc/aliases broken_sasl_auth_clients = yes command_directory = /usr/sbin config_directory = /etc/postfix daemon_directory = /usr/libexec/postfix data_directory = /var/lib/postfix debug_peer_level = 2 home_mailbox = Maildir/ html_directory = no inet_interfaces = all mail_owner = postfix mailbox_command = mailq_path = /usr/bin/mailq.postfix manpage_directory = /usr/share/man mydestination = $myhostname, $mydomain, localhost.$mydomain, localhost, /etc/postfix/dominios.cf mydomain = crver.net myhostname = server.crver.net mynetworks = 127.0.0.0/8 newaliases_path = /usr/bin/newaliases.postfix queue_directory = /var/spool/postfix readme_directory = /usr/share/doc/postfix-2.6.6/README_FILES relay_domains = #mydestination sample_directory = /usr/share/doc/postfix-2.6.6/samples sendmail_path = /usr/sbin/sendmail.postfix setgid_group = postdrop smtp_connect_timeout = 0 smtp_tls_note_starttls_offer = yes smtp_use_tls = yes smtpd_banner = $myhostname ESMTP smtpd_error_sleep_time = 0 smtpd_helo_required = yes smtpd_recipient_restrictions = permit_sasl_authenticated,permit_mynetworks,reject_unauth_destination smtpd_sasl_auth_enable = yes smtpd_sasl_authenticated_header = yes smtpd_sasl_local_domain = smtpd_sasl_security_options = noanonymous smtpd_tls_CAfile = /etc/postfix/ssl/cacert.pem smtpd_tls_auth_only = no smtpd_tls_cert_file = /etc/postfix/ssl/smtpd.crt smtpd_tls_key_file = /etc/postfix/ssl/smtpd.key smtpd_tls_loglevel = 1 smtpd_tls_received_header = yes smtpd_tls_security_level = may smtpd_tls_session_cache_timeout = 3600s smtpd_use_tls = yes strict_rfc821_envelopes = yes tls_random_source = dev:/dev/urandom unknown_local_recipient_reject_code = 550
Saludos !