Category: Anti-Spam

Postfix woes with IPv6

Since adding IPv6 capabilities to our spam scanning system, we have had a handful of issues with customers running Postfix mail servers. In some versions of Postfix, the software will try to get a quad A records (AAAA) whether or not the mail server has IPv6 connectivity. This error will be highlighted by messages like:

Network Is Unreachable

There are a couple of options, but the easiest option is to force Postfix to run in IPv4 only by editing the /etc/postfix/mail.cf and ensuring the line starting with inet_protocols is:

inet_protocols=ipv4

This will ensure the system only asks for ipv4 (A) records and should resolve the issue.

AntiSpam: NJABL being shutdown

The ‘NJABL’ (Not Just Another Bogus List) has started the process of shutting down. This list is used by many spam filtering services and email systems to form part of a score or sometimes to outright block email based upon its source ip address. It is highly recommended that all email servers should stop using this system as soon as possible. Currently the zones have been emptied, however when the system actually gets switched off, performance on email servers as they try to connect constantly to the non existent service will suffer. Spamassassin – one the most popular open source spam fighting tools still has NJABL it its current version and its current updates so administrators using install and forget anti-spam should investigate the issue further. There are details on the Spamassassin wiki on how to ‘retire’ an individual DNSBL.

More details about NJABL and its shutdown can be found here: www.njabl.org

Further information on Gconnect’s own ‘Gscanner’ anti-spam system can be found here: www.gconnect.net/anti-virus-anti-spam.php

=== UPDATE ===

The Spamassassin update channel has now retired the tests, so if you are updating regularly, then there is no need to do anything else.

Gscanner Spam Scanning service update

We have now completed testing and implementation of the Spamhaus drop lists into the Gscanner service. The drop lists contain ip addresses and net blocks which are in use by hijackers using old redundant ip ranges to launch spam from. These net block are left over from when companies go out of business and stop using them, however the RIR (Regional Internet Registry) is not informed so the ranges are kind of available to the unscrupulous! Any emails originating from these listed net blocks are rejected, however we do allow the mail transaction to go far enough to make a note of who the email was for and who it was from. Customers will see these rejections as ‘SPAMHAUS DROP LIST’ in the status graphs.

We hope this will further enhance the effectiveness of the anti-spam scanning service, further improvements will also be posted here. Details of the Anti-Spam service can be found here: http://www.gconnect.net/anti-virus-anti-spam.php.