I do shared hosting, so users should be able to use any ISP to connect. postconf -Mf :
smtp inet n - n - - smtpd submission inet n - n - - smtpd -o smtpd_tls_security_level=may -o smtpd_sasl_auth_enable=yes -o smtpd_client_restrictions=permit_sasl_authenticated,reject -o milter_macro_daemon_name=ORIGINATING smtps inet n - n - - smtpd -o smtpd_tls_wrappermode=yes -o smtpd_sasl_auth_enable=yes -o smtpd_client_restrictions=permit_sasl_authenticated,reject -o milter_macro_daemon_name=ORIGINATING pickup fifo n - n 60 1 pickup cleanup unix n - n - 0 cleanup qmgr fifo n - n 300 1 qmgr tlsmgr unix - - n 1000? 1 tlsmgr rewrite unix - - n - - trivial-rewrite bounce unix - - n - 0 bounce defer unix - - n - 0 bounce trace unix - - n - 0 bounce verify unix - - n - 1 verify flush unix n - n 1000? 0 flush proxymap unix - - n - - proxymap proxywrite unix - - n - 1 proxymap smtp unix - - n - - smtp relay unix - - n - - smtp -o smtp_fallback_relay= showq unix n - n - - showq error unix - - n - - error retry unix - - n - - error discard unix - - n - - discard local unix - n n - - local virtual unix - n n - - virtual lmtp unix - - n - - lmtp anvil unix - - n - 1 anvil scache unix - - n - 1 scache postconf -nf: authorized_submit_users = root, creta body_checks = regexp:/usr/local/etc/postfix/body_checks command_directory = /usr/local/sbin config_directory = /usr/local/etc/postfix daemon_directory = /usr/local/libexec/postfix data_directory = /var/db/postfix debug_peer_level = 2 debugger_command = PATH=/bin:/usr/bin:/usr/local/bin:/usr/X11R6/bin xxgdb $daemon_directory/$process_name $process_id & sleep 5 default_destination_concurrency_limit = 2 default_destination_rate_delay = 1s default_extra_recipient_limit = 10 header_checks = regexp:/usr/local/etc/postfix/header_checks html_directory = /usr/local/share/doc/postfix inet_protocols = ipv4 mail_owner = postfix mailq_path = /usr/local/bin/mailq manpage_directory = /usr/local/man message_size_limit = 25600000 myhostname = server8.cretaforce.gr <http://server8.cretaforce.gr/> mynetworks_style = host newaliases_path = /usr/local/bin/newaliases queue_directory = /var/spool/postfix readme_directory = /usr/local/share/doc/postfix sample_directory = /usr/local/etc/postfix sender_dependent_relayhost_maps = hash:/usr/local/etc/postfix/sender_transport sendmail_path = /usr/local/sbin/sendmail setgid_group = maildrop smtp_bind_address = 178.63.64.86 smtp_destination_concurrency_limit = 2 smtp_destination_rate_delay = 1s smtp_extra_recipient_limit = 10 smtp_tls_CAfile = /etc/ssl/certs/cacert.crt smtp_tls_cert_file = /etc/ssl/certs/server8.pem smtp_tls_key_file = /etc/ssl/private/server8.pem smtp_tls_security_level = may smtp_tls_session_cache_database = btree:$data_directory/smtp_tls_session_cache smtpd_banner = $myhostname smtpd_delay_reject = yes smtpd_helo_required = yes smtpd_helo_restrictions = permit_mynetworks, permit_sasl_authenticated, reject_non_fqdn_hostname, reject_invalid_hostname, permit smtpd_recipient_restrictions = check_sender_access hash:/usr/local/etc/postfix/sender_access, check_recipient_access hash:/usr/local/etc/postfix/recipient_access, permit_sasl_authenticated, reject_non_fqdn_sender, reject_non_fqdn_recipient, reject_unknown_recipient_domain, reject_unauth_destination, reject_unauth_pipelining, reject_invalid_hostname, reject_rbl_client zen.spamhaus.org <http://zen.spamhaus.org/>, reject_rbl_client bl.spamcop.net <http://bl.spamcop.net/>, reject_rbl_client cbl.abuseat.org <http://cbl.abuseat.org/>, permit smtpd_relay_restrictions = permit_sasl_authenticated, defer_unauth_destination smtpd_sasl_auth_enable = yes smtpd_sasl_authenticated_header = yes smtpd_sasl_local_domain = $myhostname smtpd_sasl_path = /var/run/dovecot/auth-client smtpd_sasl_type = dovecot smtpd_sender_restrictions = reject_unlisted_sender, permit_sasl_authenticated, reject_non_fqdn_sender, reject_unknown_sender_domain, permit smtpd_tls_CAfile = /etc/ssl/certs/cacert.crt smtpd_tls_ask_ccert = yes smtpd_tls_cert_file = /etc/ssl/certs/server8.pem smtpd_tls_key_file = /etc/ssl/private/server8.pem smtpd_tls_loglevel = 1 smtpd_tls_received_header = yes smtpd_tls_security_level = may smtpd_tls_session_cache_database = btree:$data_directory/smtpd_tls_session_cache tls_random_source = dev:/dev/urandom transport_maps = hash:/usr/local/etc/postfix/recipient_transport unknown_local_recipient_reject_code = 550 virtual_alias_maps = hash:/usr/local/etc/postfix/virtual virtual_gid_maps = hash:/usr/local/etc/postfix/virtual_uids virtual_mailbox_base = /home/mail virtual_mailbox_domains = hash:/usr/local/etc/postfix/domains virtual_mailbox_limit = 1000000000 virtual_mailbox_limit_inbox = no virtual_mailbox_limit_maps = hash:/usr/local/etc/postfix/vquota virtual_mailbox_limit_override = yes virtual_mailbox_maps = hash:/usr/local/etc/postfix/vmailbox virtual_maildir_extended = yes virtual_minimum_uid = 100 virtual_overquota_bounce = yes virtual_uid_maps = hash:/usr/local/etc/postfix/virtual_uids
