outgoing mail not sent since installing opendkim (I'm running centos 6.3 with Plesk)

From: Tracy Wise <tracywise_at_hotmail.com>
Date: Thu, 17 Jan 2013 06:53:37 +0000

Hi, I kind of urgently need to get a linux box up and running for a production site. I've successfully installed and configured everything except one thing: DKIM signing of outgoing mail. I actually have already installed it, set up the private and public key and all that, but the emails aren't going out.
I think I can tell you here most everything you need to know:
It's a CentOS 6.3 server from 1&1 Internet, with Plesk 11.0.9 pre-installed. For mail it uses PostFix 2.8.4.
I thought I could do everything from Plesk, but I soon discovered that Plesk doesn't support DKIM, only the obsolete "DomainKeys" (not to be confused with the newer DKIM). So I have followed the cookbook instructions at the following URL for setting up OpenDKIM with Postfix on CentOS 6.3:
(I'll refer to that from here on as the "cookbook instructions".)
Unfortunately, these cookbook instructions didn't work for me, even though I tried to follow it intelligently and not blindly, since there were some small differences with my system. Anyway now no email is sent out by my PHP test script, which simply uses the PHP mail() function. (It did indeed work before installing and configuring OpenDKIM.) Everything's installed, the OpenDKIM service is running, Postfix is running, but emails don't go out.
I'm guessing that those instructions don't work for me because of the differences with my system: Plesk, and perhaps something related to sendmail (which I'll explain in a moment). Regarding Plesk, well I've read somewhere about Plesk changing Postfix settings or adding settings in master.cf and main.cf, so maybe that's the problem.
And if it matters, let me mention here that there is an option in Plesk to enable DomainKeys signing of outgoing mail. It is unchecked by default and I have left it unchecked. I assume it should stay unchecked because, as I said at the beginning, that option in Plesk is regarding the older "DomainKeys", not DKIM.
The cookbook instructions recommended using "tail -f /var/log/maillog" to see what is happening when mail is sent, when opendkim starts, stops, or postfix starts or stops. Well, it shows nothing, even when postfix or opendkim is restarted. And that file /var/log/maillog remains empty.
Something else I discovered may also be of interest: rsyslog is getting flooded with these messages:
Jan 16 21:51:53 webcamchurch rsyslogd-2177: imuxsock lost 9524 messages from pid 3260 due to rate-limitingJan 16 21:51:53 webcamchurch rsyslogd-2177: imuxsock begins to drop messages from pid 22771 due to rate-limiting
Those two PID's (2177 and 22771) are opendkim processes.
Also note "webcamchurch" in the syslog messages: that is my DKIM selector, so I assume that's what it's referring to since I don't use that exact text for anything else.
Some other things you might want to know.
In my php.ini, sendmail path is "/usr/sbin/sendmail -t -i" HOWEVER I noticed that on my system "/usr/sbin/sendmail" isn't actually sendmail. It's an alias pointing to "/etc/alternatives/mta", which in turn points to "/usr/sbin/sendmail.postfix". So I assume PHP is actually using sendmail.postfix. (And actually I could see Postfix in the headers of emails sent out when it was working before I installed OpenDKIM.) But if it matters, let me also point out the following:
In the cookbook instructions, I had to do "yum install sendmail-devel openssl-devel" just to get some libraries needed by opendkim. Then after installing opendkim it instructed me to do "chkconfig --del sendmail" to "stop sendmail from starting on CentOS". However I DIDN'T do that step simply because on my system /usr/sbin/sendmail is actually an alias for /usr/sbin/sendmail.postfix. So I omitted that step. (Perhaps that's where I went wrong??? But I'm afraid that "chkconfig --del sendmail" will remove my sendmail alias to sendmail.postfix and I'm afraid to do that.)
Okay so I think my problem relates to one or both of the following:
1. Something to do with interference from sendmail (but please be sure you understand what I explained about my /usr/sbin/sendmail actually being an alias for /usr/sbin/sendmail.postfix so maybe that's not the problem, *shrug*).
2. [Perhaps more likely] Plesk customizes Postfix with some special settings in master.cf and main.cf. Maybe there's something there that needs to be changed?
In summary, the cookbook instructions didn't work for me, probably because of the difference in my system.
Oh, this may also be helpful to know. Though messages aren't actually sent out from the server now (since installing opendkim), I can see each message in the maildrop at /var/spool/postfix/maildrop.
So, is my problem something that can be easily fixed?
P.S. I also have a firewall with most ports blocked but outgoing mail was working before installing opendkim so I assume it's not a firewall issue, unless dkim requires some additional port (and I assume that's not the case).
Received on Thu Jan 17 2013 - 06:53:51 PST

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