There are a number of things you can do to make managing a sendmail site efficient. A number of management tools are provided in the sendmail package; let's look at the most important of these.
Mail is queued in the /var/spool/mqueue directory before being transmitted. This directory is called the mail spool. The sendmail program provides the mailq command as a means of displaying a formatted list of all spooled mail messages and their status. The /usr/bin/mailq command is a symbolic link to the sendmail executable and behaves identically to:
# sendmail -bp
The output of the mailq command displays the message ID, its size, the time it was placed in the queue, who sent it, and a message indicating its current status. The following example shows a mail message stuck in the queue with a problem:
$ mailq
Mail Queue (1 request)
--Q-ID-- --Size-- -----Q-Time----- ------------Sender/Recipient------------
RAA00275 124 Wed Dec 9 17:47 root
(host map: lookup (tao.linux.org.au): deferred)
terry@tao.linux.org.auThis message is still in the mail queue because the destination host IP address could not be resolved.
To force sendmail to immediately process the queue, issue the /usr/bin/runq command. sendmail will process the mail queue in the background. The runq command produces no output, but a subsequent mailq command will tell you if the queue is clear.
If you use a temporary dial-up Internet connection with a fixed IP address and rely on an MX host to collect your mail while you are disconnected, you will find it useful to force the MX host to process its mail queue soon after you establish your connection.
A small perl program is included with the sendmail distribution that makes this simple for mail hosts that support it. The etrn script has much the same effect on a remote host as the runq command has on the local server. If we invoke the command as shown in this example:
# etrn vstout.vbrew.comwe force the host vstout.vbrew.com to process any mail queued for our local machine.
Typically you'd add this command to your PPP startup script so that it is executed soon after your network connection is established.
sendmail collects data on the volume of mail traffic and some information on the hosts to which it has delivered mail. There are two commands available to display this information, mailstats and hoststat.
The mailstats command displays statistics on the volume of mail processed by sendmail. The time at which data collection commenced is printed first, followed by a table with one row for each configured mailer and one showing a summary total of all mail. Each line presents eight items of information, which are described in Table 12-5.
|
Field |
Meaning |
|---|---|
|
The mailer (transport protocol) number | |
|
The number of messages received from the mailer | |
|
The Kbytes of mail from the mailer | |
|
The number of messages sent to the mailer | |
|
The Kbytes of mail sent to the mailer | |
|
The number of messages rejected | |
|
The number of messages discarded | |
|
The name of the mailer |
A sample of the output of the mailstats command is shown in Example 12-7.
# /usr/sbin/mailstats
Statistics from Sun Dec 20 22:47:02 1998
M msgsfr bytes_from msgsto bytes_to msgsrej msgsdis Mailer
0 0 0K 19 515K 0 0 prog
3 33 545K 0 0K 0 0 local
5 88 972K 139 1018K 0 0 esmtp
= = = = = = = = = = = = = = = = = = = = = = = = = = = = =
= = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
T 121 1517K 158 1533K 0 0This data is collected if the StatusFile option is enabled in the sendmail.cf file and the status file exists. The StatusFile option is defined in the generic Linux configuration and therefore defined in the vstout.cf file we built from the generic configuration, as shown below:
$ grep StatusFile vstout.cf
O StatusFile=/etc/mail/statisticsTo restart the statistics collection, make the statistics file zero length and restart sendmail.
The hoststat command displays information about the status of hosts to which sendmail has attempted to deliver mail. The hoststat command is equivalent to invoking sendmail as:
sendmail -bh
The output presents each host on a line of its own, and for each the time since delivery was attempted to it, and the status message received at that time.
Persistent host status is maintained only if a path for the status directory is defined by the HostStatusDirectory option, which in turn is defined in the m4 macro configuration file by confHOST_STATUS_DIRECTORY. By default, no path is defined for the host status directory and no persistent host status is maintained.
Example 12-8 shows the sort of output you can expect from the hoststat command. Note that most of the results indicate successful delivery. The result for earthlink.net, on the other hand, indicates that delivery was unsuccessful. The status message can sometimes help determine the cause of the failure. In this case, the connection timed out, probably because the host was down or unreachable at the time delivery was attempted.
# hoststat
-------------- Hostname ---------- How long ago ---------Results---------
mail.telstra.com.au 04:05:41 250 Message accepted for
scooter.eye-net.com.au 81+08:32:42 250 OK id=0zTGai-0008S9-0
yarrina.connect.com.a 53+10:46:03 250 LAA09163 Message acce
happy.optus.com.au 55+03:34:40 250 Mail accepted
mail.zip.com.au 04:05:33 250 RAA23904 Message acce
kwanon.research.canon.com.au 44+04:39:10 250 ok 911542267 qp 21186
linux.org.au 83+10:04:11 250 IAA31139 Message acce
albert.aapra.org.au 00:00:12 250 VAA21968 Message acce
field.medicine.adelaide.edu.au 53+10:46:03 250 ok 910742814 qp 721
copper.fuller.net 65+12:38:00 250 OAA14470 Message acce
amsat.org 5+06:49:21 250 UAA07526 Message acce
mail.acm.org 53+10:46:17 250 TAA25012 Message acce
extmail.bigpond.com 11+04:06:20 250 ok
earthlink.net 45+05:41:09 Deferred: Connection timeThe purgestat command flushes the collected host data and is equivalent to invoking sendmail as:
# sendmail -bHThe statistics will continue to grow until you purge them. You might want to periodically run the purgestat command to make it easier to search and find recent entries, especially if you have a busy site. You could put the command into a crontab file so it runs automatically, or just do it yourself occasionally.