Spamassassin on Major Hayden

Fixing broken DNS lookups in spamassassin

major@mhtx.net (Major Hayden) — Fri, 20 Jun 2014 13:20:56 +0000

I talked about the joys of running my own mail server last week only to find that my mail server was broken yesterday. Spamassassin stopped doing DNS lookups for RBL and SPF checks.

I had one of these moments:

My logs looked like this:

plugin: eval failed: available_nameservers: No DNS servers available!
plugin: eval failed: available_nameservers: No DNS servers available!
rules: failed to run NO_DNS_FOR_FROM RBL test, skipping:
 (available_nameservers: [...] No DNS servers available!)
 (available_nameservers: [...] No DNS servers available!

My /etc/resolv.conf was correct and had two valid DNS servers listed. Also, the permissions set on /etc/resolv.conf were reasonable (0644) and the SELinux context applied to the file was appropriate (net_conf_t). Everything else on the system was able to resolve DNS records properly. Even an strace on the spamd process showed it reading /etc/resolv.conf successfully!

It was Google time. I put some snippets of my error output into the search bar and found a spamassassin bug report. Mark Martinec found the root cause of the bug:

Net::DNS version 0.76 changed the field name holding a set of nameservers in a Net::DNS::Resolver object: it used to be ’nameservers’, but is now split into two fields: ’nameserver4’ and ’nameserver6'.

Mail/SpamAssassin/DnsResolver.pm relied on the internal field name of a Net::DNS::Resolver object to obtain a default list of recursive name servers, so the change in Net::DNS broke that.

The patch from the bug report worked just fine on my Fedora 20 mail server. Be sure to restart spamd after making the change.

There’s a Fedora bug report as well.

If anyone is interested, I plan to write up my email configuration on Fedora soon for other folks to use. I might even make some ansible playbooks for it. ;)

Fedora update: Fedora’s spamassassin package has been updated to 3.4.0-7 and it fixes two bugs. You’ll find it in the stable repositories in a few days.

Basic procmail configuration with spamassassin filtering

major@mhtx.net (Major Hayden) — Wed, 13 Aug 2008 17:00:48 +0000

I’ve used this extremely basic procmail configuration a million times, and it’s a great start for any server configuration. It passes e-mails through spamassassin (if they’re smaller than 256KB) and then filters any e-mail marked as spam to /dev/null:

LOGFILE=/var/log/procmail.log
DROPPRIVS=yes</p>
<p>:0fw
| /usr/bin/spamc</p>
<p>:0
* ^X-Spam-Status: Yes
/dev/null

Of course, you can make this much more complicated with some additional customization.

High iowait on RHEL 4 with Plesk and SpamAssassin

major@mhtx.net (Major Hayden) — Thu, 31 Jan 2008 18:38:58 +0000

One of my biggest complaints on RHEL 4 is the large resource usage by the version of SpamAssassin that is installed. When it runs, it uses a ton of CPU time and causes a lot of disk I/O as well. When running top, you may see multiple spamd processes. For a high-volume e-mail server (like the one I administer), this is simply unacceptable.

I decided to do something about it, and here are the steps:

First, you will need two RPMs:

Latest SpamAssassin RPM from Dag

The psa-spamassassin RPM from SWSoft/Parallels.

Once you have them both on the server, install the new SpamAssassin package from Dag:

# rpm -Uvh spamassassin-(version).el4.rf.(arch).rpm

At this point, Plesk’s spamassassin scripts will be non-functional, but the next step will fix it:

# rpm -Uvh --force psa-spamassassin-(version).(arch).rpm

NOTE: DO NOT REMOVE the psa-spamassassin RPM. This will begin stripping your system of all SpamAssassin configurations and it cannot be reversed!

Plesk’s SpamAssassin scripts have been restored at this point in the process. Now, we need to do the part that really makes SpamAssassin work efficiently:

# sa-update; sa-compile;

This will update the SpamAssassin rules, and it will compile the rules with re2c (you may also need to get this RPM from Dag). This compilation means less disk access, and less CPU time being used to process e-mails.

To activate the compiled rules within SpamAssassin, uncomment the plugin line in /etc/mail/spamassassin/v320.pre:

# Rule2XSBody - speedup by compilation of ruleset to native code<br /> #<br /> loadplugin Mail::SpamAssassin::Plugin::Rule2XSBody

Please bear in mind that this process is done at your own risk. This may cause issues getting support from SWSoft or your hosting company. This has been tested on Red Hat Enterprise Linux 4 64-bit with Plesk 8.1.1, 8.2.0, and 8.2.1 with SpamAssassin 3.2.3 and 3.2.4.