Centos – Telling sendmail to auth

Where are the logs?

The default location depends on your linux/unix system, but the most common places are

• /var/log/maillog
• /var/log/mail.log
• /var/adm/maillog
• /var/adm/syslog/mail.log

If it's not there, look up /etc/syslog.conf. You should see something like this

mail.*         -/var/log/maillog

sendmail writes logs to the mail facility of syslog. Therefore, which file it gets written to depends on how syslog was configured.

If you system uses syslog-ng (instead of the more "traditional" syslog), then you'll have to look up your syslog-ng.conf file. You'll should something like this:

# This files are the log come from the mail subsystem.
#
destination mail     { file("/var/log/mail.log"); };
destination maillog  { file("/var/log/maillog"); };
destination mailinfo { file("/var/log/mail.info"); };
destination mailwarn { file("/var/log/mail.warn"); };
destination mailerr  { file("/var/log/mail.err"); };

Unable to send out emails?

One of the most common reason I've seen for a freshly installed sendmail not being able to send out emails is the DAEMON_OPTIONS being set to listen only on 127.0.0.1

See /etc/mail/sendmail.mc

dnl #
dnl # The following causes sendmail to only listen on the IPv4 loopback address
dnl # 127.0.0.1 and not on any other network devices. Remove the loopback
dnl # address restriction to accept email from the internet or intranet.
dnl #
DAEMON_OPTIONS(`Port=smtp,Addr=127.0.0.1, Name=MTA')dnl

If that's your case, remove the "Addr=127.0.0.1" part, rebuild your conf file and you're good to go!

DAEMON_OPTIONS(`Port=smtp, Name=MTA')dnl

[root@server]$ m4 sendmail.mc > /etc/sendmail.cf
[root@server]$/etc/init.d/sendmail restart

If you've been making changes to /etc/sendmail.cf manually thus far (instead of the *.m4 file) you can make similar changes in /etc/sendmail.cf. The offending line will look like this:

O DaemonPortOptions=Port=smtp,Addr=127.0.0.1, Name=MTA

Change it to:

O DaemonPortOptions=Port=smtp, Name=MTA

What I did to disable local delivery. I'll be using the example.com domain.

Requirements:

• example.com A entry pointing to IP address assigned to one of the eth interfaces.
• /etc/hosts defining example.com assigned to the very same IP address as above
• example.com MX records pointing to Google servers (ASPMX.L.GOOGLE.COM, etc)
• default sendmail installation (mine was on Ubuntu)

Steps:

vim /etc/mail/sendmail.mc

at the end:

define(`MAIL_HUB', `example.com.')dnl
define(`LOCAL_RELAY', `example.com.')dnl

and then:

sendmailconfig (or /etc/mail/make depending on your distro)
service sendmail restart

testing:

echo -e "To: user@example.com\nSubject: Test\nTest\n" | sendmail -bm -t -v
echo -e "To: user\nSubject: Test\nTest\n" | sendmail -bm -t -v

You should see it connecting to the google server and then you should see your mail being delivered to your Google inbox.