Даю команду в FreeBSD:

echo "Tel..." | mail -s "Sale house" korbnik@mail.ru

В журнале maillog вводятся записи:

Oct 10 10:49:58 nika sm-mta[1003]: starting daemon (8.14.3): SMTP+queueing@00:30:00
Oct 10 10:49:58 nika sm-msp-queue[1007]: starting daemon (8.14.3): queueing@00:30:00
Oct 10 11:10:33 nika sendmail[1341]: o9A7AXsr001341: from=root, size=95, class=0, nrcpts=1, msgid=<201010100710.o9A7AXsr001341@nika.korbnik.ru>, relay=root@localhost
Oct 10 11:10:33 nika sm-mta[1342]: o9A7AXNY001342: from=<root@nika.korbnik.ru>, size=414, class=0, nrcpts=1, msgid=<201010100710.o9A7AXsr001341@nika.korbnik.ru>, proto=ESMTP, daemon=IPv4, relay=localhost [127.0.0.1]
Oct 10 11:10:33 nika sendmail[1341]: o9A7AXsr001341: to=korbnik@mail.ru, ctladdr=root (0/0), delay=00:00:00, xdelay=00:00:00, mailer=relay, pri=30095, relay=[127.0.0.1] [127.0.0.1], dsn=2.0.0, stat=Sent (o9A7AXNY001342 Message accepted for delivery)
Oct 10 11:10:34 nika sm-mta[1344]: o9A7AXNY001342: to=<korbnik@mail.ru>, ctladdr=<root@nika.korbnik.ru> (0/0), delay=00:00:01, xdelay=00:00:01, mailer=esmtp, pri=30414, relay=mxs.mail.ru. [94.100.176.20], dsn=5.0.0, stat=Service unavailable
Oct 10 11:10:34 nika sm-mta[1344]: o9A7AXNY001342: o9A7AYNY001344: DSN: Service unavailable
Oct 10 11:10:34 nika sm-mta[1344]: o9A7AYNY001344: to=<root@nika.korbnik.ru>, delay=00:00:00, xdelay=00:00:00, mailer=local, pri=31438, relay=local, dsn=2.0.0, stat=Sent

И в итоге в ящик root-а вот что приходит:

From MAILER-DAEMON Sun Oct 10 11:10:34 2010
Return-Path: <MAILER-DAEMON@nika.korbnik.ru>
Received: from localhost (localhost)
    by nika.korbnik.ru (8.14.3/8.14.3) id o9A7AYNY001344;
    Sun, 10 Oct 2010 11:10:34 +0400 (MSD)
    (envelope-from MAILER-DAEMON)
Date: Sun, 10 Oct 2010 11:10:34 +0400 (MSD)
From: Mail Delivery Subsystem <MAILER-DAEMON>
Message-Id: <201010100710.o9A7AYNY001344@nika.korbnik.ru>
To: <root@nika.korbnik.ru>
MIME-Version: 1.0
Content-Type: multipart/report; report-type=delivery-status;
    boundary="o9A7AYNY001344.1286694634/nika.korbnik.ru"
Subject: Returned mail: see transcript for details
Auto-Submitted: auto-generated (failure)

This is a MIME-encapsulated message

--o9A7AYNY001344.1286694634/nika.korbnik.ru

The original message was received at Sun, 10 Oct 2010 11:10:33 +0400 (MSD)
from localhost [127.0.0.1]

   ----- The following addresses had permanent fatal errors -----
<korbnik@mail.ru>
    (reason: 550 Unroutable address)

   ----- Transcript of session follows -----
... while talking to mxs.mail.ru.:
>>> MAIL From:<root@nika.korbnik.ru> SIZE=414

<<< 550 Unroutable address
554 5.0.0 Service unavailable

--o9A7AYNY001344.1286694634/nika.korbnik.ru
Content-Type: message/delivery-status

Reporting-MTA: dns; nika.korbnik.ru
Received-From-MTA: DNS; localhost
Arrival-Date: Sun, 10 Oct 2010 11:10:33 +0400 (MSD)

Final-Recipient: RFC822; korbnik@mail.ru
Action: failed
Status: 5.0.0
Diagnostic-Code: SMTP; 550 Unroutable address
Last-Attempt-Date: Sun, 10 Oct 2010 11:10:34 +0400 (MSD)

--o9A7AYNY001344.1286694634/nika.korbnik.ru
Content-Type: message/rfc822

Return-Path: <root@nika.korbnik.ru>
Received: from nika.korbnik.ru (localhost [127.0.0.1])
    by nika.korbnik.ru (8.14.3/8.14.3) with ESMTP id o9A7AXNY001342
    for <korbnik@mail.ru>; Sun, 10 Oct 2010 11:10:33 +0400 (MSD)
    (envelope-from root@nika.korbnik.ru)
Received: (from root@localhost)
    by nika.korbnik.ru (8.14.3/8.14.3/Submit) id o9A7AXsr001341
    for korbnik@mail.ru; Sun, 10 Oct 2010 11:10:33 +0400 (MSD)
    (envelope-from root)
Date: Sun, 10 Oct 2010 11:10:33 +0400 (MSD)
From: Charlie Root <root@nika.korbnik.ru>
Message-Id: <201010100710.o9A7AXsr001341@nika.korbnik.ru>
To: korbnik@mail.ru
Subject: Sale house

Tel. 8(926)529-70-35. Foto - http://korbnik.narod.ru/

--o9A7AYNY001344.1286694634/nika.korbnik.ru--

Выход в интернет есть, sendmail настроен по умолчанию и запущен.
Чего ему не нравится?

Заранее благодарен. Борис.