Pushing an Email Message in Mail Queue

Computer History Notes - Herong's Tutorial Notes

∟1983 - "Sendmail" Mail Transfer Agent Developed by Eric Allman

∟Pushing an Email Message in Mail Queue

This section provides an example using Sendmail a Mail User Agent (MUA) to transfer a remote email message, which is stored in the mail queue waiting for a connection to the remote machine.

On the Internet, not all machines are reachable all the time. Sendmail use a mail queue to manage emails for remote machine that not reachable. Here is an example session of using Sendmail as a MUA to transfer a remote email to a machine that is not reachable:

$su root

#rm /var/log/mail.log
#rm /var/spool/mail/herong
#rm /var/spool/mqueue/*
#sendmail -X /var/log/mail.log -v herong@hotmail.com
herong@hotmail.com... hotmail.com: Name server timeout
herong@hotmail.com... Transient parse error -- message queued
                      for future delivery
From: root@darkstar.home.com
To: herong@hotmail.com
Subject: Second Test

Hi. This is another test.
.
herong@hotmail.com... queued
#

#more /var/log/mail.log
00088 <<< herong@hotmail.com... hotmail.com: Name server timeout
00088 <<< herong@hotmail.com... Transient parse error -- message queued
                                for future delivery
00088 <<< From: root@darkstar.home.com
00088 <<< To: herong@hotmail.com
00088 <<< Subject: Second Test
00088 <<<
00088 <<< Hi. This is another test.
00088 <<< .
00088 <<< herong@hotmail.com... queued

#ls /var/spool/mqueue
dfUAA00088   qfUAA00088
#more /var/spool/mqueue/dfUAA00088
Hi. This is another test.
#more /var/spool/mqueue/qfUAA00088
V2
T1216860066
K1216860066
N1
P30100
/I3/1/158
Mhost map: lookup (hotmail.com) deferred
Fb
$ root@localhost
$root
RPFD:herong@hotmail.com
H?P?Return-Path: <root>
HReceived: (from root@localhost)
      by darkstar.home.com (8.9.0/8.9.0) id UAA00088
      for herong; Thu, 23 Jul 1998 12:35:29
H?D?Date: Thu, 23 Jul 1998 12:35:29
H?x?Full-Name: System Admin
H?M?Message-Id: <199807230041.UAA00088@darkstar.home.com>
HFrom: root@darkstar.home.com
HTo: herong@hotmail.com
HSubject: Second Test
.

Notice that:

"-X" and "-v" options help us how Sendmail works on an email message for a local email address.
The "hotmail.com: Name server timeout" message tells us that machine hotmail.com is not reachable.
On a Linux system, the default location of the Sendmail queue is /var/spool/mqueue.