Requeuing Mail For Problem Domains Or Hosts That Are Down

Define The `reque` Mailer In The Standard /`etc/sendmail.cf` file

#####################################
###   Reque Mailer specification   ###
#####################################

# Pass these messages back to sendmail with alternate queue directory
# Use SMTP to pass the message back to a second sendmail daemon
# listening to port 26 (or some other unused port) on this host $j
# Note the k mailer flag to disable the smtp loopback check
Mreque,		P=[IPC], F=kmDFMuXa, S=11/31, R=11/31, E=\r\n, L=2040,
		T=DNS/RFC822/SMTP,
		A=IPC $j 26
                
# No mailer specific rulesets because mailer uses esmtp mailer rulesets

You may also want to add the reque name to the /etc/services file

/etc/services:
smtp		25/tcp		mail
reque		26/tcp		mail

If you do this the A= line can use reque rather than 26:

		A=IPC $j reque

Define Problem Domains For The Reque Mailer

# Class $={RequeDoms} is the parent domains that we are having SMTP
#	delivery problems with
# Pass these messages back to sendmail by using SMTP to connect to port 26
# Define these within the sendmail.cf file itself
C{RequeDoms} aol.com
# Define these in a separate file
F{RequeDoms} -o /etc/mail/RequeDoms

# macro $P is for requeuing mail for a specific host or domain
# by manually invoking sendmail:
#       sendmail -q -v -MPproblem.domain
# This macro is not defined in the sendmail.cf file

Pass Mail For Problem Domains To Reque Mailer

In ruleset S0 (S98 would be a logical choice)

# Requeue mail for recipient addresses to problem domains $=R by
#       passing them to the reque mailer which calls sendmail with
#       an alternate mqueue directory

R$* < @$={RequeDoms} . > $*		$#reque $@ $2$3 $:$1<@$3.>$4
R$* < @$+ . $={RequeDoms} . > $*		$#reque $@ $2$3 $:$1<@$2.$3.>$4

Requeue Mail For Problem Domains From The Command Line

If you want to be able to reque mail for a specific host or domain by manually invoking sendmail add this in ruleset S0 (again S98 would be a logical choice)

# Reque mail for a specific host or domain defined by manually invoking
# sendmail with -oMPproblem.dom or -MPproblem.dom

# Test if macro $P has been set
R$+ < @$+ > 		$: $1 < @$2 @$P > 

# If noting after second @ sign, $P not set, strip second @
R$+ < @$+ @ > 		$1 < @$2 > 

# Other wise $P had a value, test if recipient domain ends with $P
R$+ < @ $P . @$P > 		$#reque $@$P $:$1 < @ $P. >
R$+ < @$+ .$P . @$P > 		$#reque $@$2.$P $:$1 < @ $2.$P. >
R$+ < @ $P @$P > 		$#reque $@$P $:$1 < @ $P >
R$+ < @$+ . $P @$P > 		$#reque $@$2.$P $:$1 < @ $2.$P >

# Recipient domain did not end with $P, strip second @ $P in address
R$+ < @$+ @$P >		$1 < @$2 >

Then to requeue to a specific problem domain run:

	sendmail -q -MPprodigy.com

Or run it as an queue daemon:

	sendmail -q10m -MPprodigy.com

Create The Reque `sendmail.cf` File

Copy the original sendmail.cf file without the previous changes:
cp /etc/sendmail.cf.orig /etc/sendmail.cf.reque

Change the SMTP daemon options to listen to another port (port 26 is a logical choice)

# SMTP daemon options
#OOPort=esmtp
O DaemonPortOptions=Port=26

Change the mqueue directory to spool the mail in a different directory

# queue directory
#OQ/var/spool/mqueue
O QueueDirectory=/var/spool/mqueue.reque

Change the default delivery mode to queue

# default delivery mode
#Odbackground
O DeliveryMode=queue

Change the queue sort order to host

# shall we sort the queue by hostname first?
O QueueSortOrder=host

Optionally change the sendmail.cf file version number to reflect alternate config file

# Configuration version number
DZ-reque

Test The New Configuration

Start the new requeue sendmail daemon
/usr/sbin/sendmail -bd -q15m-C/etc/sendmail.cf.reque

Check you syslog file

If you get the error message:
Jun 11 22:58:47 firewall sendmail[26027]: problem creating SMTP socket
Jun 11 22:58:52 sendmail[26027]: NOQUEUE: SYSERR(root):opendaemonsocket: cannot bind: Address already in use

Then you have not set the DaemonPortOption correctly and are binding to port 25

Next kill and restart the standard sendmail daemon:

Check for both sendmail daemons:

	ps -ax | grep sendmail

Normal SMTP server:

	2608	??	Ss	0:00.08 accepting connections on port 25 (sendmail)

Requeue SMTP server:

	2619	??	Ss	0:00.06 accepting connections on port 26 (sendmail)

telnet firewall 25
Trying 192.102.231.125 ...
Connected to firewall.harker.com.
Escape character is '^]'.
220 firewall.harker.com ESMTP Sendmail /8.8.8 ready at Wed, 11 Jun 1997 23:20:50 GMT
helo harker.harker.com
250 firewall.harker.com Hello harker.harker.com [192.102.231.1], pleased to meet you
mail from: user@example.com
250 user@example.com... Sender ok
verb
250 Verbose mode
onex
250 Only one transaction
rcpt to: userID@aol.com
250 userID@aol.com... Recipient ok
data
354 Enter mail, end with "." on a line by itself
from: user@example.com
to: userID@aol.com

test
.
050 userID@aol.com... Connecting to firewall.harker.com port 26 via reque...
050 220 firewall.harker.com ESMTP Sendmail /8.8.8-reque ready at Wed, 11 Jun 1997 23:21:50 GMT
050 >>> EHLO firewall.harker.com
050 250-firewall.harker.com Hello root@firewall.harker.com [192.102.231.125], pleased to meet you
050 250-EXPN
050 250-VERB
050 250-8BITMIME
050 250-SIZE
050 250-DSN
050 250-ONEX
050 250-ETRN
050 250-XUSR
050 250 HELP
050 >>> MAIL From:<user@example.com> SIZE=63
050 250 <user@example.com>... Sender ok
050 >>> RCPT To:<userID@aol.com>
050 250 <userID@aol.com>... Recipient ok
050 >>> DATA
050 354 Enter mail, end with "." on a line by itself
050 >>> .
050 250 XAA26203 Message accepted for delivery
050 userID@aol.com... Sent (XAA26203 Message accepted for delivery)
250 XAA26200 Message accepted for delivery
050 Closing connection to firewall.harker.com
050 >>> QUIT
050 221 firewall.harker.com closing connection
quit
221 firewall.harker.com closing connection

Check The Reque Directory With `mailq`

Use the -oQ/var/spool/mqueue.reque command line flag to print the messages in the reque queue directory
sendmail -bp -oQ/var/spool/mqueue.reque
or mailq -oQ/var/spool/mqueue.reque

mailq -oQ/var/spool/mqueue.reque

	Mail Queue (1 request)
--Q-ID--	--Size--	-----Q-Time-----	---------Sender/Recipient--------
XAA26203	8	Wed Jun 11 23:21	<user@example.com>
lt;userID@aol.com>

Finally, modify the host's startup scripts to start the reque SMTP daemon

/etc/rc.local:
/usr/sbin/sendmail -bd -q11m-C/etc/sendmail.cf.reque

Putting These Changes Into M4

To put the reque mailer and the reque mailer delivery into a M4 template file you would precede the mailer definition itself with:

MAILER_DEFINTIONS

You would precede the delivery rules with:
LOCAL_RULE_0

You would create the reque alternate sendmail.cf file by defining the M4 macros to change the options:

A M4 HACK template for the reque mailer and delivery rulesets can be found at:

ftp://ftp.harker.com/pub/sendmail/cf/reque.m4

To add the reque mailer to your sendmail.cf file you would download

the template either the hack or feature sub-directory of the sendmail-8.X/cf directory. If you were going to add the reque mailer as a M4 HACK or FEATURE the file would be called:

	hack/reque.m4

In your host.mc file or feature/reque.m4

This template would be included in your sendmail.cf file by including:

	HACK(reque)
or	FEATURE(reque)

in your host.mc file.

A host.mc template for the reque daemon itself can be found at: ftp://ftp.harker.com/pub/sendmail/cf/reque.mc

To use this template you would need to change the OSTYPE to match your OS.

Remeber this is the sendmail.cf file for your reque daemon, not the sendmail.cf for your normal prot 25 sendmail daemon.

Just another "Harker's Helpful Hint" from Harker systems

Define The reque Mailer In The Standard /etc/sendmail.cf file