Friday, May 16, 2008

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E-mail Delivery Problems: A Tale of Blacklists and Outbound Spam Filtering

By Shari Worthington
President

To blacklist someone means to deny them certain privileges or services, or to deny them work in a particular field or cast them out from a particular social circle. Whatever it is, it isn’t a particularly fun place to be. But it’s worse when the blacklisting happens in cyberspace. On the Internet, a blacklist is a means of controlling access to specified computers and servers. The blacklist contains information related to the IP addresses or e-mail addresses or software that is not allowed into the system. Everything else is allowed to pass through.

Blacklists have become an important tool for ISPs, as they are all desperately trying to keep their servers from being overwhelmed by a sea of spam. And don’t doubt for a minute that spam is a problem. According to Barracuda Networks, a spam firewall developer, only 6-8% of all e-mail they see in any day is allowed to pass through. The rest is tagged as some form of spam that gets thrown into the virtual circular file long before it gets to anyone’s desktop.

Figure 1. Barracuda Networks, Processed E-mail, 10-11 March 2007

Pay Attention to Details

The problem is that even legitimate e-mail marketers can find themselves on a blacklist. This happens when the e-mail sender has done something unwanted and, as a result, attracted negative attention. In some cases, the negative attention is an e-mail recipient complaining; in other cases, you may have set up the e-mail incorrectly and caught the attention of a corporate spam filter.

Most ISPs will ignore the occasional crank complaint. But if you regularly get complaints or fail to fix structural problems with your e-mail, you will eventually get an ISPs attention. In some cases (but not all), they will let you know there is an issue you need to resolve. If you don’t, you may find yourself on a blacklist.

Then your nightmare begins. There are hundreds of blacklists and, once on them, there’s no easy way to get off. You either avoid getting on them in the first place by using good e-mail practices, or you fix the problem afterwards and end up making thousands of phone calls to beg and plead your case to the blacklist owners and ISPs.

Find out if your server is blacklisted at http://www.mxtoolbox.com/blacklists.aspx. [NOTE: we have no experience with MX’s services, but we like this blacklist search function.]

Outbound Spam Filters

And the situation keeps getting more challenging. Not only do you have to worry about getting your e-mail in through corporate and desktop spam filters, now you also have to worry about outbound spam filters. We discovered the existence of this new type of firewall when we tried to forward an e-mail from one of the major automation magazines. Turns out, our ISP wouldn’t forward the message because it considered it spam.

I was surprised. It was just a standard trade magazine newsletter with links to articles and a few advertisers. But our ISP had installed a new outbound spam filter, which stopped the e-mail dead in its tracks because the IP address was blacklisted.

Outbound spam filters are firewalls that check the e-mail leaving an ISP and traveling on to another computer destination. These devices have been adopted by many ISPs as a way to stop spoofing and phishing and other nasty spam techniques whereby someone steals your domain’s identity and uses it to blanket the world with messages you would never ever be caught sending.

Our ISP happens to use Barracuda Networks for its outbound spam filtering. We discovered that Barracuda has blacklisted not just the one automation magazine, but the top three automation magazines! This is happening either because the magazines aren’t promptly resolving customer requests to be removed (which I doubt because they’re all very careful about that these days), or the magazines’ third-party e-mail service is improperly formatting the e-mails.

Either way, they’ve got a big problem. If we know these magazines’ e-mails are getting caught in the outbound spam filter because they’ve been blacklisted, then it’s highly likely that they’re also being caught in the inbound spam filter and are rarely reaching their intended destination. As a result, their open rates and click-throughs are going to be only a fraction of what they could be.

So be proactive. Use legit e-mail service providers, ones who know what they’re doing and do not have any blacklisted IP addresses. Consider also investigating how to whitelist your e-mail newsletter. Whitelists are used when IT wants to block all e-mail, except that which appears on this list of acceptable IP addresses. You can start with CleanMyMailbox.

For more information on how to make sure your e-mail marketing is getting where it’s supposed to, see Telesian’s e-newlsetter service.