Spam Traps 101

Over the past months I’ve run an occasional series on email marketing nomenclature. Recently it was brought to my attention that though I’ve frequently mentioned the term “spam trap,” many marketers don’t know precisely what that means. This month, I intend to correct that omission with a guide to spam traps.

What Are Spam Traps?

A spam trap is a seemingly valid email address used to identify spam messages. The idea is to take an address (even an entire domain) that hasn’t been subscribed to any email and monitor the email it receives. As it wasn’t subscribed to any email, anything it receives must be unsolicited, hence spam.

In practice, which addresses are spam traps, where they come from, and how they’re used vary enormously. For an address to be useful, it must receive some amount of email. Apart from addresses designed to catch dictionary attacks (define), this generally means the address must have been publicized somewhere. Common sources for spam traps are addresses that were once used to post to Usenet or used as role addresses (e.g., hostmaster@, noc@) in such areas as domain registrations. In some situations, addresses that were once valid but have had a period of invalidity are repurposed as spam traps.

Why Do They Matter?

Many organizations use spam traps. They include DNS (define) blocklists, large ISPs, many spam filter providers, and email reputation organizations. The specifics of how the spam traps are utilized vary from organization to organization, even from spam trap to spam trap. Some organizations rate the value of their traps based on their previous usage; others look for hits on multiple traps; and still others use them only in an advisory capacity along with other metrics.

Generally speaking, hitting a spam trap (that is, sending an email message to it) can lead, directly or indirectly, to being blocklisted by the trap’s operator. Organizations known to use spam traps include SpamCop, Passive Spam Block List (PSBL), Brightmail, and most large ISPs.

How Did One Get on Our List?

Generally speaking, good list hygiene and maintenance practices will prevent spam traps ever joining your list. How a spam trap came to be on your list depends on the type of trap. Typical mechanisms include:

  • Poor list sources. If you harvest addresses, purchase them, use email append services, or even fail to maintain permission information for your list, you risk adding spam traps to your list. Though no reputable organization uses address harvesting, list purchase, e-append, and permission maintenance problems are disturbingly common.
  • List poisoning. This may be deliberate or accidental. If you run an unconfirmed list (single opt-in or notified opt-in), someone could deliberately add a spam trap address to your list, or enter what he considers to be a bogus address that happens to be a spam trap. It’s not uncommon for organizations to register common misspellings of popular domains and use those domains as spam traps. Avoid this problem by utilizing confirmed opt-in and never coercing registrations.
  • List ageing. Once-valid addresses and domains can sometimes be repurposed as spam traps. If you go for a long period without mailing to an address, it may be used in this manner. Additionally, if you fail to perform effective bounce management, an invalid address may remain on your list and subsequently become a spam trap.

How Do We Remove Them?

Spam traps are, by definition, secret. This makes removal extremely difficult. You could ask the operator what the address is, but it’s unlikely she’ll tell you. You could throw away your entire list and start from scratch, but this is not usually a practical option.

This leaves repermissioning your list. Send a message requiring subscribers to reconfirm their desire to be on the list by clicking on a link or responding to the message. This isn’t ideal. It’s inconvenient to valid subscribers. And inevitably, some don’t reconfirm, even though they wish to remain on the list.

Problems with reconfirmation can be mitigated if you can identify clean list segments. Such segments won’t require a reconfirmation message. Verifying a given segment is clean depends on accurate information about when a spam trap is hit, which may or may not be available.

Removing spam traps from lists is difficult and time-consuming. It’s far better to ensure they don’t get on your lists in the first place. This can be achieved by consistently applying good address collection and permission maintenance practices.

Until next time…

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

Related reading