[Prefer]

для начала покажите
postconf -n

[EndErr]

alias_database = hash:/usr/local/etc/postfix/aliases
broken_sasl_auth_clients = yes
command_directory = /usr/local/sbin
config_directory = /usr/local/etc/postfix
content_filter = smtp-amavis:[127.0.0.1]:10024
daemon_directory = /usr/local/libexec/postfix
data_directory = /var/db/postfix
debug_peer_level = 2
header_checks = regexp:/usr/local/etc/postfix/header_checks
html_directory = no
inet_interfaces = all
mail_owner = postfix
mailbox_size_limit = 52428800
mailq_path = /usr/local/bin/mailq
manpage_directory = /usr/local/man
message_size_limit = 10485760
mime_header_checks = regexp:/usr/local/etc/postfix/mime_header_checks
mydestination = $mydomain, $myhostname, localhost.$mydomain
mydomain = testdomain.org
myhostname = srv3.testdomain.org
mynetworks = 127.0.0.0/8, 192.168.1.0/24
mynetworks_style = host
myorigin = $mydomain
newaliases_path = /usr/local/bin/newaliases
queue_directory = /var/spool/postfix
readme_directory = no
receive_override_options = no_address_mappings
sample_directory = /usr/local/etc/postfix
sendmail_path = /usr/local/sbin/sendmail
setgid_group = maildrop
smtp_tls_note_starttls_offer = yes
smtp_use_tls = yes
smtpd_client_restrictions =
smtpd_etrn_restrictions = permit_mynetworks, reject
smtpd_helo_restrictions =
smtpd_recipient_restrictions = permit_mynetworks, permit_sasl_authenticated, reject_unauth_destination, reject_unauth_pipeling, check_client_access hash:/usr/local/etc/postfix/access_client, check_client_access pcre:/usr/local/etc/postfix/access_client.pcre, reject_unknown_client_hostname, check_helo_access hash:/usr/local/etc/postfix/access_helo, reject_invalid_helo_hostname, reject_non_fqdn_helo_hostname, reject_unknown_helo_hostname, check_sender_access hash:/usr/local/etc/postfix/access_sender, reject_non_fqdn_sender,reject_unknown_sender_domain, reject_unverified_sender, reject_non_fqdn_recipient_domain, reject_unknown_recipient_domain, reject_unverified_recipient, reject_rbl_client cbl.abuseat.org, reject_rbl_client dnsbl.njabl.org, reject_rbl_client combined.njabl.org, reject_rbl_client dul.ru, reject_rbl_client dynablock.njabl.org, reject_rbl_client opm.blitzed.org, reject_rhsbl_client blackhole.securitysage.com, reject_rhsbl_client rhsbl.sorbs.net, reject_rhsbl_sender blackhole.securitysage.com, reject_rhsbl_sender rhsbl.sorbs.net, permit
smtpd_sasl_auth_enable = yes
smtpd_sasl_local_domain = $mydomain
smtpd_sasl_security_options = noanonymous
smtpd_sender_restrictions =
smtpd_tls_CAfile = /usr/local/etc/postfix/smtpd.pem
smtpd_tls_auth_only = yes
smtpd_tls_cert_file = /usr/local/etc/postfix/smtpd.pem
smtpd_tls_key_file = /usr/local/etc/postfix/smtpd.pem
smtpd_tls_loglevel = 1
smtpd_tls_received_header = yes
smtpd_tls_session_cache_timeout = 3600s
smtpd_use_tls = yes
tls_random_source = dev:/dev/urandom
unknown_local_recipient_reject_code = 550

[Аlchemist]

Попробуйте отключить все антиспамовые приблуды и свести к минимуму все ограничения.
Если заработает, то потом добавить по очереди все, что вырубалось.

[EndErr]

а подскажите плиз, для корпоративного почтового сервера для внутреннего и внешнего пользования нужны 2 сетевухи или одна справится с заданной цели?

[Аlchemist]

а подскажите плиз, для корпоративного почтового сервера для внутреннего и внешнего пользования нужны 2 сетевухи или одна справится с заданной цели? »

А сами попробуйте на этот вопрос ответить, зачем вам каждая сетевая карта?