The sendmail that just wouldn’t

Today, I came across the strangest problem I’d ever seen in years of administering sendmail. Normally, sendmail is very much set-and-forget, taking care of emails without any problems. Obviously, today wasn’t normal.

No, not at all. The server had sendmail installed, and properly configured, but wouldn’t send any emails. It’s as if it wasn’t even running.

ps -fea | grep sendmail

Nope, no sendmail. So, let’s start sendmail and check again.

/sbin/service sendmail start

Uh oh. The usual start up messages didn’t appear. Checking if sendmail was running again showed 0 sendmail instances.

After looking through /var/log/message and finding nothing about sendmail anywhere, as well as a stubbornly empty /var/log/maillog, I decided the sendmail binary must be corrupt so issued

yum reinstall sendmail

After yum downloaded and installed the new RPM, I was sure that sendmail would start right up without any problems. I start the service and… nothing happens.

Out of frustration, I decided to run sendmail on the terminal and see where it was failing.

[root@server ~]$ /usr/sbin/sendmail
bash: /usr/sbin/sendmail: No such file or directory

Well, that couldn’t be right. bash had even auto-completed that for me. sendmail had to be installed, as all the other files where there. Wait a minute….

[root@server ~]$ ls -l /usr/sbin/sendmail
lrwxrwxrwx 1 root root 21 May 30 11:51 /usr/sbin/sendmail -> /etc/alternatives/mta

Most modern servers include alternatives to help manage different programs that provide the same feature. This is accomplished through the /etc/alternatives directory that has symlinks to the actual binaries, as well as /var/lib/alternatives to configure the entire system, which is managed by /usr/sbin/alternatives.

The only problem on the server turned out to be a broken link, /etc/alternatives/mta, which was pointing to a nonexistant qmail installation. The entire problem was fixed by issuing

/usr/sbin/alternatives --set mta /usr/sbin/sendmail.sendmail

I wasn’t happy with this, as it wasn’t “autoconfigured” by alternatives automatically, so I copied /var/lib/alternatives/mta from an identical server that only has sendmail running and ran

/usr/sbin/alternatives --auto mta

alternatives properly detected sendmail, fixed the symlinks in /etc/alternatives and sendmail successfully launched.

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