>Полный лог приёма и пересылки письма наружу покажите. И желательно с реальными
>доменами и ip-адресами. Плюс все записи из master.cf с командой smtp.
>
>
>ОС кстати какая?

mail# cat /usr/local/etc/postfix/master.cf
#
# Postfix master process configuration file.  For details on the format
# of the file, see the master(5) manual page (command: "man 5 master").
#
# Do not forget to execute "postfix reload" after editing this file.
#
# ==========================================================================
# service type  private unpriv  chroot  wakeup  maxproc command + args
#               (yes)   (yes)   (yes)   (never) (100)
# ==========================================================================
smtp      inet  n       -       n       -       -       smtpd
#submission inet n       -       n       -       -       smtpd
#  -o smtpd_tls_security_level=encrypt
#  -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
#628      inet  n       -       n       -       -       qmqpd
pickup    fifo  n       -       n       60      1       pickup
cleanup   unix  n       -       n       -       0       cleanup
qmgr      fifo  n       -       n       300     1       qmgr
#qmgr     fifo  n       -       n       300     1       oqmgr
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
# When relaying mail as backup MX, disable fallback_relay to avoid MX loops
#relay     unix  -       -       n       -       -       smtp
        -o smtp_fallback_relay=
#       -o smtp_helo_timeout=5 -o smtp_connect_timeout=5
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
#
# ====================================================================
# Interfaces to non-Postfix software. Be sure to examine the manual
# pages of the non-Postfix software to find out what options it wants.
#
# Many of the following services use the Postfix pipe(8) delivery
# agent.  See the pipe(8) man page for information about ${recipient}
# and other message envelope options.
# ====================================================================
#
# maildrop. See the Postfix MAILDROP_README file for details.
# Also specify in main.cf: maildrop_destination_recipient_limit=1
#
#maildrop  unix  -       n       n       -       -       pipe
#  flags=DRhu user=vmail argv=/usr/local/bin/maildrop -d ${recipient}
#
# ====================================================================
#
# The Cyrus deliver program has changed incompatibly, multiple times.
#
#old-cyrus unix  -       n       n       -       -       pipe
#  flags=R user=cyrus argv=/cyrus/bin/deliver -e -m ${extension} ${user}
#
# ====================================================================
#
# Cyrus 2.1.5 (Amos Gouaux)
# Also specify in main.cf: cyrus_destination_recipient_limit=1
#
#cyrus     unix  -       n       n       -       -       pipe
#  user=cyrus argv=/cyrus/bin/deliver -e -r ${sender} -m ${extension} ${user}
#
# ====================================================================
#
# See the Postfix UUCP_README file for configuration details.
#
#uucp      unix  -       n       n       -       -       pipe
#  flags=Fqhu user=uucp argv=uux -r -n -z -a$sender - $nexthop!rmail ($recipient)
#
# ====================================================================
#
# Other external delivery methods.
#
#ifmail    unix  -       n       n       -       -       pipe
#  flags=F user=ftn argv=/usr/lib/ifmail/ifmail -r $nexthop ($recipient)
#
#bsmtp     unix  -       n       n       -       -       pipe
#  flags=Fq. user=bsmtp argv=/usr/local/sbin/bsmtp -f $sender $nexthop $recipient
#
#scalemail-backend unix -       n       n       -       2       pipe
#  flags=R user=scalemail argv=/usr/lib/scalemail/bin/scalemail-store
#  ${nexthop} ${user} ${extension}
#
#mailman   unix  -       n       n       -       -       pipe
#  flags=FR user=list argv=/usr/lib/mailman/bin/postfix-to-mailman.py
#  ${nexthop} ${user}

ОС: FreeBSD 7.0

лог письма принятого письма:

From - Thu Apr 02 16:29:06 2009
X-Account-Key: account8
X-UIDL: UID59-1225550229
X-Mozilla-Status: 0001
X-Mozilla-Status2: 10000000
X-Mozilla-Keys:                                                                                
Return-Path: <>
X-Original-To: yura@somonair.com
Delivered-To: yura@somonair.com
Received: by mail.somonair.com (Postfix)
    id 0B2D71A9B90; Thu,  2 Apr 2009 16:33:04 +0500 (TJT)
Date: Thu,  2 Apr 2009 16:33:04 +0500 (TJT)
From: MAILER-DAEMON@somonair.com (Mail Delivery System)
Subject: Undelivered Mail Returned to Sender
To: yura@somonair.com
Auto-Submitted: auto-replied
MIME-Version: 1.0
Content-Type: multipart/report; report-type=delivery-status;
    boundary="081ED1A9B8D.1238671984/mail.somonair.com"
Content-Transfer-Encoding: 8bit
Message-Id: <20090402113304.0B2D71A9B90@mail.somonair.com>

This is a MIME-encapsulated message.

--081ED1A9B8D.1238671984/mail.somonair.com
Content-Description: Notification
Content-Type: text/plain; charset=us-ascii

This is the mail system at host mail.somonair.com.

I'm sorry to have to inform you that your message could not
be delivered to one or more recipients. It's attached below.

For further assistance, please send mail to postmaster.

If you do so, please include this problem report. You can
delete your own text from the attached returned message.

                   The mail system

<yuriy.agarkov@gmail.com>: mail for gmail.com loops back to myself

Домен: somonair.com
IP: 71.200.217.51

>Полный лог приёма и пересылки письма наружу покажите. И желательно с реальными
>доменами и ip-адресами. Плюс все записи из master.cf с командой smtp.
>
>
>ОС кстати какая?

Apr  3 12:10:26 mail postfix/smtpd[29494]: connect from somonair.com[91.200.217.51]
Apr  3 12:10:26 mail postfix/smtp[29499]: warning: host gmail-smtp-in.l.google.com[216.239.59.27]:25 greeted me with my own hostname mail.somonair.com
Apr  3 12:10:26 mail postfix/smtp[29499]: warning: host gmail-smtp-in.l.google.com[216.239.59.27]:25 replied to HELO/EHLO with my own hostname mail.somonair.com
Apr  3 12:10:26 mail postfix/smtp[29499]: 30C961A9A7C: to=<yuriy.agarkov@gmail.com>, relay=gmail-smtp-in.l.google.com[216.239.59.27]:25, delay=1.5, delays=0.31/0.01/1.1/0, dsn=5.4.6, status=bounced (mail for gmail.com loops back to myself)
Apr  3 12:10:26 mail postfix/smtpd[29494]: disconnect from somonair.com[91.200.217.51]
Apr  3 12:10:26 mail postfix/cleanup[29497]: 9F8F01A9B4C: message-id=<20090403071026.9F8F01A9B4C@mail.somonair.com>
Apr  3 12:10:26 mail postfix/bounce[29500]: 30C961A9A7C: sender non-delivery notification: 9F8F01A9B4C
Apr  3 12:10:26 mail postfix/qmgr[28069]: 9F8F01A9B4C: from=<>, size=2709, nrcpt=1 (queue active)
Apr  3 12:10:26 mail postfix/qmgr[28069]: 30C961A9A7C: removed
Apr  3 12:10:26 mail postfix/virtual[29501]: 9F8F01A9B4C: to=<yura@somonair.com>, relay=virtual, delay=0.02, delays=0/0.01/0/0.01, dsn=2.0.0, status=sent (delivered to maildir)

>Юр, я там подключился и все разрешилось. Все работает, в общем.

Спасибо большое! Я тут не обратил внимания на элементарную весчь :)
telnet какой-нибудь_почтарь 25
возвращается приветствие моего же сервера, т.е. роутер не выпускает 25 порт.
В постфиксе оказывается оказывается все ок.
Подобная проблема решается или явным прописыванием прокси сервера в main.conf или копанием в сторону роутера.
Всем спасибо за ответы!