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I'm using sendmail version 8.14.4 on Fedora 15 to send email. My Rails app uses delayed_job to queue up emails. Messages will queue up in /var/spool/mqueue as expected, but don't always get processed. I can see the messages and sendmail is definitely running in the background. Restarting the process does nothing. However, when I issue the sendmail -q command, sendmail gets to work and starts sending. The really odd thing is that this behavior only occurs sometimes. Other times message queue up and are delivered as expected.

I've tried tweaking various sendmail configs to reduce the time between queue processing (for example, adding define('confMIN_QUEUE_AGE', '0')dnl to /etc/mail/, but nothing seems to do the trick. Any ideas what might be the root cause?

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"running in the background" isn't enough of a description. Tell us what options your Sendmail queue runner daemons are running with. – JdeBP Jun 2 '11 at 23:24
@JdeBP, thanks for the response. I'm fairly new to the underpinnings of sendmail. Would this be something from the config files that you're looking for? I essentially have done nothing other than turn on the default Fedora sendmail service, i.e., service sendmail start. – markmcb Jun 2 '11 at 23:30
It's the choices that you've made in this area that are important. – JdeBP Jun 2 '11 at 23:38
@JdeBP, yeah, that's what I was reading when I set MinQueueAge=0 as I mentioned. (I also tried various other short intervals.) I'm not sure if there's something else I should config in addition to this. – markmcb Jun 3 '11 at 0:01
You still haven't put what you have already configured in your question. Again: Tell us what options your Sendmail queue runner daemons are running with. – JdeBP Jun 3 '11 at 9:31

On my FC15 box:

ps auxw | fgrep sendmail
root      1803  ... sendmail: accepting connections
smmsp     1812  ... sendmail: Queue runner@01:00:00 for /var/spool/clientmqueue

You have two bg sendmail's: the first one is for incomng mail, the second runs the queue once a hour. You can tweak the time between runs by changing the settings found in /etc/sysconfig/sendmail (15 minutes is a favorite value).

The stuff is for other purposes (see the README file in the package sendmail-config)

Note that - for a stock sendmail config - messages end up in the queue only if they cannot be delivered right away (because e.g. they are greylisted, or the destinaton server is down, or too busy, etc.), So very frewquent queue runs usually don't help much.

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