Without use of any of the optional DBM tables, sendmail+IDA delivers mail via the DEFAULT_MAILER (and possibly RELAY_HOST and RELAY_MAILER) in the m4 file used to generate sendmail.cf. It is easily possible to override this behavior through entries in the domaintable or uucpxtable.
Forcing mail to be transferred via UUCP
In an ideal world (from the Internet perspective), all hosts have records in the Domain Name Service (DNS) and will send mail with fully qualified domain names.
If you happen to talk via UUCP to such a site, you can force mail to go through the point-to-point direct UUCP connection rather than through your default mailer by essentially 'undomainizing' their hostname through the uucpxtable. The result is that sendmail will then determine (via UUCPNODES in the sendmail.cf m4 file) that you are directly connected to the remote system and will queue the mail for delivery with UUCP.
# (in the uucpxtable) # un-domainize sys2.com to force UUCP delivery sys2 sys2.com
Preventing mail from being delivered via UUCP
The opposite condition also occurs. Frequently, systems may have a number of direct UUCP connections that are used infrequently or that are not as reliable and always available as the default mailer or relay host.
For example, in the Seattle area there are a number of systems that exchange the various Linux distributions via anonymous uucp when the distributions are released. These systems talk UUCP only when necessary, so it is generally faster and more reliable to send mail through multiple very reliable hops and common (and always available) relay hosts rather than through unreliable direct point-to-point UUCP links.
It is easily possible to prevent UUCP delivery of mail to a host that you are directly connected to. If the remote system is domainized, you can add an entry in the domaintable that will fully domainize the hostname, and prevent a match by the UUCPNODES line in the sendmail.cf m4 file. The result is generally that mail will go via the relay_mailer and relay_host (or default_mailer).
# (in domaintable) # prevent mail delivery via uucp to a neighbor uucp_neighbor.domain.com uucp_neighbor
To process queued messages immediately, merely type '/usr/lib/runq' which will invoke sendmail with the appropriate options to cause sendmail to run through the queue of pending jobs immediately rather than waiting for the next scheduled run.
Building and testing sendmail.cf
cd to $LIBDIR/CF (generally /usr/local/lib/mail/CF)
copy the example.m4 file to yourhostname.m4
edit it to do the right thing (set your relay, hostname,pseudonymns, etc.)
test that dude...
/usr/lib/sendmail -bt -Cyourhostname.cfat the '>' prompt, try:
"3,0 me" "3,0 my-uucp-neighbor!foo" "3,0 firstname.lastname@example.org" "3,0 mynode!me" "3,0 email@example.com"(all should “do the right thing” hopefully)
put it into place as /etc/sendmail.cf
start up sendmail as a daemon
/usr/lib/sendmail -bd -q1h
put the above line in the /etc/rc.local file so sendmailstarts up routinely when the system boots.
Sendmail comes with a utility called 'mailstats' that reads a file called /usr/local/lib/mail/sendmail.st file and reports the number of messages and number of bytes transferred by each of the mailers used in the senmail.cf file. This file must be created by the local administrator manually for sendmail logging to occur. The running totals are cleared by removing and recreating the sendmail.st file. One way is to do the following:
cp /dev/null /usr/local/lib/mail/sendmail.st
Probably the best way to do quality reporting regarding who uses mail and how much volume passes to, from, and through the local system is to turn on mail debugging with syslogd. Generally, this means running the /etc/syslogd daemon from your system startup file with a line in /etc/syslog.conf that looks something like the following:
The sendmail.st file does not grow enough to be a concern. If you use mail.debug and get any medium to high mail volume, the syslog output can get quite large. Output files from syslogd generally need to be rotated or purged on a routine basis from cron.
There are a number of commonly available utilities that can summarize the output of mail logging from syslog. One of the more well known utilities is the syslog-stat.pl file that is distributed with the sendmail+IDA sources.
Fast/Flexible Linux OS Recovery
On Demand Now
In this live one-hour webinar, learn how to enhance your existing backup strategies for complete disaster recovery preparedness using Storix System Backup Administrator (SBAdmin), a highly flexible full-system recovery solution for UNIX and Linux systems.
Join Linux Journal's Shawn Powers and David Huffman, President/CEO, Storix, Inc.
Free to Linux Journal readers.Register Now!
- The Italian Army Switches to LibreOffice
- Download "Linux Management with Red Hat Satellite: Measuring Business Impact and ROI"
- Linux Mint 18
- Oracle vs. Google: Round 2
- Varnish Software's Varnish Massive Storage Engine
- The FBI and the Mozilla Foundation Lock Horns over Known Security Hole
- Devuan Beta Release
- Privacy and the New Math
- Ben Rady's Serverless Single Page Apps (The Pragmatic Programmers)
Until recently, IBM’s Power Platform was looked upon as being the system that hosted IBM’s flavor of UNIX and proprietary operating system called IBM i. These servers often are found in medium-size businesses running ERP, CRM and financials for on-premise customers. By enabling the Power platform to run the Linux OS, IBM now has positioned Power to be the platform of choice for those already running Linux that are facing scalability issues, especially customers looking at analytics, big data or cloud computing.
￼Running Linux on IBM’s Power hardware offers some obvious benefits, including improved processing speed and memory bandwidth, inherent security, and simpler deployment and management. But if you look beyond the impressive architecture, you’ll also find an open ecosystem that has given rise to a strong, innovative community, as well as an inventory of system and network management applications that really help leverage the benefits offered by running Linux on Power.Get the Guide