Linux Mail-Queue mini-HOWTO
Leif Erlingsson, leif@lege.com, Jan P Tietze, jpti�
etze@mail.hh.provi.de
v2.03, 2001-12-17, sendmail 8.8.7
Queue Remote Mail + Deliver Local Mail The Configuration Changes Nec�
cessary to Make Sendmail Deliver Local Mail ***Now*** While Stashing
Remote Mail in The Queue Until "I Say So".
______________________________________________________________________
Table of Contents
1. Introduction
2. NON dial-on-demand solutions PART
2.1 Starting sendmail
2.2 Configuring sendmail
2.2.1 Configuring sendmail.cf directly, for trivial configurations
2.2.2 Configuring sendmail.cf using m4 source
2.3 Menu support suggestions
3. Dial-on-demand solutions PART
3.1 Configuring sendmail.cf
3.1.1 Configuring sendmail.cf directly, for trivial configurations
3.1.2 Configuring sendmail.cf using the m4 source.
3.2 Adding dial delay
3.2.1 Configuring sendmail.cf directly
3.2.2 Configuring sendmail.cf using m4 source
4. Delivering e-mail
4.1 How to have e-mail delivered at special times.
5. License
______________________________________________________________________
1. Introduction
The document is written by two authors. The NON dial-on-demand
solutions part (oldest part) is written by Leif Erlingsson
<leif@lege.com>, and the newer dial-on-demand solutions part is
written by Jan P Tietze <jptietze@mail.hh.provi.de>.
2. NON dial-on-demand solutions PART
Written by Leif Erlingsson <leif@lege.com>.
The original version of this part contained a lot of unnecessary
stuff. This is all it takes, really...
2.1. Starting sendmail
Slackware et al: /etc/rc.d/rc.M:
echo "Starting sendmail daemon (/usr/sbin/sendmail -bd -os) [queue only mode]..."
/usr/sbin/sendmail -bd -os # NOT "-bd -q 15m", the "standard" flags!
RedHat et al: /etc/rc.d/init.d/sendmail.init:
echo -n "Starting sendmail: [queue only mode]"
daemon sendmail -bd -os # NOT daemon sendmail -bd -q1h
The -os is not really essential, all it does is this:
SuperSafe [s] Be super-safe when running things, i.e.,
always instantiate the queue file, even if
you are going to attempt immediate delivery.
Sendmail always instantiates the queue file
before returning control the client under
any circumstances. This should really
always be set.
This should already be configured in the default sendmail.cf anyway.
2.2. Configuring sendmail
Serious sendmail users use the m4 source for this. I recommend this
solution if you ever plan on upgrading sendmail and also make anything
but trivial changes to sendmail.cf.
If you never intend to fix sendmail so envelope return headers et al
works even though you might be on dynamic dial in IP or something,
then you may not need to get the m4 source.
2.2.1. Configuring sendmail.cf directly, for trivial configurations
This way of doing things is extremeley version dependent vs.
sendmail.cf versions. The following solution is *only* valid for
sendmail-8.8.x.
Edit /etc/sendmail.cf:
# avoid connecting to "expensive" mailers on initial submission?
O HoldExpensive=True
... later ...
##### @(#)smtp.m4 8.33 (Berkeley) 7/9/96 #####
Msmtp, P=[IPC], F=mDFMuXe, S=11/31, R=21, E=\r\n, L=990,
T=DNS/RFC822/SMTP,
A=IPC $h
Mesmtp, P=[IPC], F=mDFMuXae, S=11/31, R=21, E=\r\n, L=990,
T=DNS/RFC822/SMTP,
A=IPC $h
Msmtp8, P=[IPC], F=mDFMuX8e, S=11/31, R=21, E=\r\n, L=990,
T=DNS/RFC822/SMTP,
A=IPC $h
Mrelay, P=[IPC], F=mDFMuXa8e, S=11/31, R=61, E=\r\n, L=2040,
T=DNS/RFC822/SMTP,
A=IPC $h
The important flag above is ``e''. Don't fuss if the other flags look
different in your file. Keep your flags as-is, only add ``e'' to your
flags according to the above examples, unless it's there already.
``e'' marks the mailers as ``expensive''.
2.2.2. Configuring sendmail.cf using m4 source
In the following I will, for simplicity, assume that the sendmail
version is 8.8.7. If you have a different version, replace 8.8.7 with
that version number below! Also, the instructions will not work for
older versions of sendmail. Get the latest sendmail!
Download the sendmail source. Try ``http://WWW.Sendmail.ORG'' or
possibly ``ftp.sendmail.org''.
I also recommend that you obtain my patch for allowing envelope sender
reverse aliasing and other nice stuff to really make you take control
over your mail environment.
Write to ``Sendmail Patch <sendmail@lege.com>'', Subject:
``sendmail-8.8.7'', if 8.8.7 is your sendmail version.
They are also available from ``http://www.lege.com'', as is the sgml
source of this mini-HOWTO!
You don't have to get my patches in order to get ``Queue Remote Mail +
Deliver Local Mail'' to work. My patches solve other things. But I
just thought this would be a nice place to mention them, as many Linux
users will find them extremely useful. (They will even give you
properly working virtual domains, if you like. The virtual domains
don't have to be ``local''. They will give you ``xaliases'', or in
other words ``reverse aliasing''.)
Unpack the sendmail source. You may get /usr/src/sendmail-8.8.7/. cd
/usr/src/sendmail-8.8.7/cf
Now overlay my patch, if you want it, otherwise skip this step: If you
don't want to use procmail as Local Delivery Agent, save away your
/usr/src/sendmail-8.8.7/cf/ostype/linux.m4 before doing this... Save
my patch to ``/tmp/sendmail-8.8.7-cf-cpio-idcmu.gz'', then...
cd /usr/src/sendmail-8.8.7/cf
gzip -dc < /tmp/sendmail-8.8.7-cf-cpio-idcmu.gz | cpio -idcmu
If you didn't want to use procmail, write back the saved copy of
/usr/src/sendmail-8.8.7/cf/ostype/linux.m4 again.
And regardless of if you applied my patch or not, you must make sure
these lines or very similar ones are added to
/usr/src/sendmail-8.8.7/cf/cf/yourhostname.smtp.mc (but if you applied
my patch you may want to investigate filenames containing the word
``elijah'', under /usr/src/sendmail-8.8.7/cf):
dnl # Defer Delivery to "expensive" mailers until next time the
dnl # queue is processed using "O HoldExpensive=True" and make
dnl # sure smtp mailers are "expensive".
dnl # (See original "sendmail" book Chapter 30: Options,
dnl # "Oc - Don't connect to expensive mailers", or
dnl # 2nd Edition "sendmail" book Chapter 34.8.29,
dnl # "HoldExpensive (c), Queue for expensive mailers".)
dnl # / Leif Erlingsson <leif@lege.com>
define(`confCON_EXPENSIVE', `True')
define(SMTP_MAILER_FLAGS, e)
MAILER(local)dnl
MAILER(smtp)dnl
2.3. Menu support suggestions
The 1.x versions of this document contained Menu support suggestions
for /var/X11R6/lib/fvwm/system.fvwmrc. I have dropped those in the
current version, but they are available on request:
Write to ``Menu support suggestions <fvwmrc@lege.com>'', Subject:
``Menu support suggestions''
3. Dial-on-demand solutions PART
Written by Jan P Tietze <jptietze@mail.hh.provi.de>.
Many Linux users access the Internet through a dialup line, and many
have decided to implement dial-on-demand facilities on their system.
That is, whenever an IP packet of some sort has to leave the local
network or the local host, the link to an Internet Service Provider
(ISP) will automatically be established. The link will be dropped
after some period of time that no packet has travelled across.
Although this is very comfortable and cost effective, there is one
special case in which this is neither comfortable (as the time to
bring up a "traditional" modem dialup is very noticeable) nor cost
effective, and this is sending e-mail. E-Mail is commonly sent by
SMTP, either delivered by your own system or through a SMTP host on
the Internet that usually resides in your ISP's network.
With dialup lines, every time you send a message the link will have to
be brought up. This is quite okay if you send only one message, but if
you happen to create and send multiple messages, bringing up the line
more than once can be tedious and cost ineffective. Also, if your ISP
imposes limits as to what times you are allowed to login, this would
also restrict you to postpone messages at certain times of the day,
and you would have to manually send them later.
Section 1 of this document will solve the situation, however in
situations where an external DNS lookup would cause the link up, the
link will still be established even if e-mail is just being queued.
The reason is that sendmail wishes to "canonify" host names.
The solution to this problem is twofold: First, we'll have to
moderately change sendmail.cf. And then we have to define the process
of actual mail delivery. Personally, I prefer to have cron do the job
for me and describe the necessary changes below.
3.1. Configuring sendmail.cf
For the reasons stated in [1.2], I recommend modifying the m4 sources
instead of editing sendmail.cf directly. It will actually save you a
lot of hassle and make configuration changes more verbose.
First, perform all the changes described in the first part of this
document. Then go through the dial-on-demand specific stuff.
3.1.1. Configuring sendmail.cf directly, for trivial configurations
Configuring directly is highly impractical and anything but verbose,
but obviously, this is your decision.
Close to very bottom of your sendmail.cf should be a line that reads:
R$* < @ $* $~P > $* $: $1 < @ $[ $2 $3 $] > $4
Precede that line with a "#" so that it reads
#R$* < @ $* $~P > $* $: $1 < @ $[ $2 $3 $] > $4
3.1.2. Configuring sendmail.cf using the m4 source.
Add the following line to
/usr/src/sendmail-8.8.7/cf/cf/yourhostname.smtp.mc:
FEATURE(nocanonify)dnl
Your final sendmail.cf can then be built by issuing the following
commands. Remember to always back up your old /etc/sendmail.cf before
installing the new one:
cp /etc/sendmail.cf /etc/sendmail.cf.bak
cd /usr/src/sendmail-8.8.7/cf/cf
m4 yourhostname.smtp.mc > /etc/sendmail.cf
3.2. Adding dial delay
It is oftentimes useful, especially when using modem lines, to have a
dial delay installed. This means that if sendmail tries to initiate a
connection in an attempt to send an e-mail (and this causes the line
to go up) but the link actually takes more time to get established
than what sendmail thinks should be a reasonable timeout, sendmail
will simply wait some seconds and then retry.
3.2.1. Configuring sendmail.cf directly
Somewhere in your sendmail.cf could be a line that would read:
#O DialDelay=10s
(or very similar). Delete the ``#''. If there's no ``#'' at the
beginning of the line, things should be considered okay (it just means
this had already been enabled before).
If there is no such line in your sendmail.cf, add one (it is a wise
thing to do to add this in the "options" part of the file):
O DialDelay=10s
Now change the ``10s'' part to the number of seconds you deem
suitable.
3.2.2. Configuring sendmail.cf using m4 source
Add the following line to
/usr/src/sendmail-8.8.7/cf/cf/yourhostname.smtp.mc:
define(`confDIAL_DELAY',`10s')
Now change the ``10s'' part to the number of seconds you deem
suitable.
Your final sendmail.cf can then be built by issuing the following
commands. Remember to always back up your old /etc/sendmail.cf before
installing the new one:
cp /etc/sendmail.cf /etc/sendmail.cf.bak
cd /usr/src/sendmail-8.8.7/cf/cf
m4 yourhostname.smtp.mc > /etc/sendmail.cf
4. Delivering e-mail
E-Mail delivery can be invoked by issuing the command "sendmail -q".
For those who are interested in what sendmail actually does, "sendmail
-q -v" will give a more verbose version of the delivery process.
It is very convenient to automate the process of e-mail delivery. A
tool commonly used for this process is cron.
4.1. How to have e-mail delivered at special times.
Edit your crontab:
crontab -e
Add lines of the form:
05 18-23,0-7 * * Mon,Tue,Wed,Thu,Fri /usr/sbin/sendmail -q
05 * * * Sat,Sun /usr/sbin/sendmail -q
Please refer to the crontab man page (available through "man 5 \
crontab") for further information. I think the format is pretty
obvious. The example crontab entries shown above send e-mail (if, and
only if, e-mail is available from the queue) 5 minutes after an hour
on weekdays, starting at 6:05 pm, and stopping at 7:05 am. On
weekends, e-mail is delivered 5 minutes after an hour, starting at
12:05 pm on Saturday, and stopping 11:05 pm on Sunday.
As a dial-on-demand user, it is sometimes desirable to have your
system collect your e-mail via the POP3 protocol at certain times of
the day. You could therefore add an entry similar to the following to
your crontab:
0 21 * * * popclient -3 -u <your pop3 user name
goes here> -p <put your password here> -o /var/spool/mail/<the user
on your system that should receive the collected e-mail>
<mailhost.somedomain.com>
Of course, this should all go on a single line.
Then, save the file and leave the editor. The crontab should now be
installed.
5. License
This document is distributed under the terms of the GNU Free
Documentation License. You should have received a copy along with it.
If not, it is available from http://www.fsf.org/licenses/fdl.html.