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Whitelists and Filters

  |  May 10, 2004   |  Comments

A whitelist is a badge of honor to e-mailers, a testament to their legitimacy. But the badge may be plastic, not gold.

E-mailers love being whitelisted by ISPs. A whitelist is an ISP-sanctioned list of mass emailer IP addresses. An ISP allows messages sent from these addresses to pass through their systems (theoretically). A whitelist is a badge of honor to emailers, testifying to their legitimacy. It means their email is delivered to recipients. Yet that badge may be plastic, not gold.

Not a Panacea

I'm not saying whitelists don't work. If you're a mass emailer, by all means, contact top-tier ISPs to ensure you're taking the right steps to get your email delivered. But I see three problems with whitelisting as we know it.

First, you're not the only emailer calling ISPs. They're inundated with calls from every emailer on the planet. All desire to be whitelisted. Most ISPs don't have a staff "whitelist manager." That role falls to system administrators and others who aren't in communications or responsible for handling emailers' phone calls. If you're lucky, they return your call. Dedication and persistence are required to resolve problems and participate with an ISP's program.

Second, whitelisting won't ensure your email is delivered. In addition to filters for bulk sender volume, most ISP filters analyze message content. Depending on copy and creative, your email could be blocked for trigger keywords such as "free," the names of prescription drugs, common URLs, attached programs, or strange images. I've seen lists of hundreds of trigger words ISPs use to block spam. Many can, of course, be used in legitimate email.

Finally, many complaints against emailers are directed at those already whitelisted. Consumers have been told repeatedly not to reply to, or unsubscribe from, spam. The philosophy has spread to anything that could be spam, with no consideration for permission-based email. Declining email open rates are largely attributable to growing numbers of recipients who don't unsubscribe.

Those same people press the "this is spam" button in their email client with abandon. If complaints against whitelisted emailers continue, ISPs will have no choice but to make whitelist requirements more stringent or (more likely) drop whitelists altogether. E-mailers and ISPs must educate consumers on the difference between permission- and non-permission-based email.

Who's Faster, You or a Spammer?

Many top email filtering minds have antivirus backgrounds. They think dynamically and continually update solutions to meet a constantly changing landscape. Spam-solution companies such as Brightmail update their systems every 20 minutes or so. Others, such as Cloudmark and Matador, update on the fly, based on user response.

List hygiene plays a role in the delivery race. Most spammers don't have actual email addresses. They create lists with directory (also called "dictionary") attacks. They email to lists, pull the bounces, then reuse the "good" addresses. Permission-based emailers remail to bounced addresses after determining the type of bounce. They try to maintain relationships for the long term, not destroy lists by emailing too frequently.

According to Return Path, the average email address lifespan is approximately three years. What happens to old, abandoned addresses? Rather than kill them, many ISPs recycle them to new users or add them to filters as "spamtrap" addresses. (A spamtrap is an email address used by a filtering service to identify spam. Many are created by filtering services and placed in public domains, such as chat rooms and message boards.) Either way, email sent to a spamtrap doesn't bounce. It's received by someone and considered spam, or sent straight into a blackhole (deleted), along with all the rest of your messages to that ISP's users. Thought cleaning your list wasn't high priority? It's mandatory.

Tips to Manage the Problem

  • Hire someone to track email delivery. Have her continually build relationships with ISPs.

  • Subscribe to end-user email filtering services, including a Brightmail-powered mailbox to check if your email is blocked.

  • Make sure your creatives are aware of filter trigger words and other creative issues.

  • Make unsubscribe language and subscription management options clear and easy to follow (more on this here).

  • Create "seed accounts" with top ISPs, and monitor email delivery. If you don't want to do this yourself, utilize a tracking and monitoring service such as Assurance Systems.

  • Consistently clean your lists. Use email change of address services to update old addresses.

Is whitelisting is effective? Have other tips to manage the filtering problem? Let me know.

Ben is off this week. Today's column ran earlier on ClickZ.

Want more email marketing information? ClickZ E-Mail Reference is an archive of all our email columns, organized by topic.


Ben Isaacson

Ben Isaacson is the privacy and compliance leader for Experian, overseeing Internet and advanced technology privacy and compliance affairs across Experian Marketing Services products including CheetahMail, Digital Advertising Services, and Hitwise. Mr. Isaacson's previous roles include serving as the executive director of the Association for Interactive Marketing (AIM), a former DMA subsidiary. He regularly blogs at EmailResponsibly.com.

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