Email Deliverability

Deliverability Indicators: Understanding Spam Traps and What They Mean For Customer Engagement

Pooja Raje and Dan Stone By Pooja Raje and Dan Stone Jun 18, 2024

No one wants to fall into a trap right? Not rats, not bears, and definitely not any good email senders. Like the saying goes, a trap is only a trap if you don't know about it. But even if you know about it, it's still a challenge! The good news is, with knowledge comes power.

In this edition of deliverability indicators, we are focusing on one of the most dreaded obstacles for email marketers: the infamous spam trap. Let’s dive into the world of spam traps to understand what they really are, the different types, how to prevent them, and much more.

What is a spam trap?

At its core, a spam trap is an email address that is created or used by mailbox providers, blocklist operators, and other anti-spam organizations to identify and catch spammers red-handed.

Alternate terms for spam traps: pristine spam traps, honeypots

Remember the first email address you ever created (which is likely long-abandoned now), a typo you made when providing your email address during sign up, or even an email address you used at a former company (which then became invalid after you embarked on your next adventure)? These dummy, fake, or erroneous email addresses are used as spam traps by mailbox providers (MPs), blocklist operators, anti-spam organizations, etc. to try to identify and catch spammers, who are heedlessly sending emails to these addresses time and again. But often, even legitimate email senders could end up with spam traps in their mailing list if they are not practicing good list hygiene and have poor list acquisition techniques.

Sending email to a spam trap is known as ‘hitting a spam trap’ and could prove detrimental to a sender’s email deliverability and sender reputation depending on the type of spam trap being hit and what organization monitors that trap.

The different types of spam traps, and their causes and consequences

Now that we know hitting a trap can impact email performance, it is also important to understand that there are a few different types of spam traps in the email world and that their impact on email deliverability and performance varies significantly. Some spam traps are more damaging to sender reputation than others.

At a high level, there are three main categories of spam traps: pristine spam traps, recycled spam traps, and typo spam traps. Let’s look at them in more detail and understand the consequences of each of them.

Pristine spam traps

Pristine spam traps are email addresses that are specifically created by ISPs, blocklists, and other security organizations with the sole purpose of catching spammers and senders with poor list hygiene. Their only function is to act as a spam trap. These email addresses have never been valid, and thus are incapable of signing up for an account or opting in to a mailing list. Pristine traps may be added to lists during the signup process by app users or site visitors who provide incorrect information to bypass a required form field or get access to gated content without divulging their correct address. The user likely doesn’t realize that they have provided a trap; they have just entered something resembling an email address quickly and without care. Purchased or rented lists also tend to contain pristine spam traps, as there is no way of validating the authenticity and quality of this purchased data. The only way such traps can enter a sender’s list is if they are collecting data and growing their subscriber list without confirming consent via double opt-in.

Hitting a pristine spam trap is a clear indicator of suspicious data acquisition methods and poor list hygiene practices. It acts as a flag for MPs to identify potentially illegitimate senders and label them as spammers. The consequences of hitting a pristine spam trap are severe and can negatively impact sender reputation. They can cause the sender’s IP address or domain to be added to a blocklist, resulting in emails being rejected or landing in the spam or junk folder. Hence, these spam traps can prove very dangerous for senders who are looking to maintain strong email deliverability and a good sender reputation.

Recycled spam traps

Recycled spam traps are email addresses that at one point in time were valid addresses that belonged to real people, but have since been abandoned by their original owners and are no longer in use now (at least not for their original purpose). Recycled traps help identify senders who are mailing to inactive users frequently and are not cleaning their email list of unengaged recipients. Some examples of recycled spam traps include: defunct domains, personal email addresses that are no longer being used, work email addresses of ex-employees, and college or university email addresses of students who already graduated and moved on. While senders might have obtained these email addresses by gaining consent initially, if they are sending email campaigns to very old email addresses and lists, they could still fall prey to this trap.

Hitting a recycled spam trap is a clear indicator that the sender is not keeping their subscriber lists healthy and up-to-date. That is, the sender is not maintaining their email list by regularly removing inactive users and email addresses, which are bouncing and returning as invalid or have ceased engaging. While the consequences of hitting recycled spam traps may not be as harmful as pristine spam trap hits, repeatedly sending emails to these addresses can make you look like a spammer, have a negative effect on sender reputation over time, and result in email deliverability issues. So the next time you want to send re-engagement campaigns to a really old list or an email campaign to your entire database, think again! Always exercise extreme caution when taking sending risks; trap hits can contribute to blocklistings that severely disrupt your marketing efforts.

Typo spam traps

As the name suggests, typo traps are common typos or misspellings of legitimate domains. These faux addresses make prime targets for trap setters and are designed to ensnare senders with poor list hygiene and data collection practices. Common examples of such typo domains include gnail, hmail, or fmail instead of gmail; hotnail instead of hotmail; yaho instead of yahoo; or ‘.con’ instead of ‘.com’. Sometimes these invalid addresses could be genuine human errors, but if they are not cleaned off the subscriber list regularly, your reputation may suffer. A typo trap may also be a pristine trap if the domain was created deliberately to discover senders engaging in poor practices.

Hitting a typo trap is an indication that a sender is not incorporating email deliverability best practices, such as double opt-in (or confirmed opt-in) to confirm their subscriber’s email subscription, nor does the sender use email engagement filters for targeting or have a sunset policy in place. These behaviors point towards unhealthy list building and list maintenance practices. However, it doesn’t necessarily indicate that the sender is a spammer or an illegitimate sender. The consequences of hitting a typo spam trap may not be as severe as a pristine spam trap, but if left ignored could lead to long term email deliverability issues and damage sender reputation over time. After all, prevention is better than cure!

Where can you see spam traps?

That’s the tricky part–you can’t! A trap is likely indistinguishable from any other email address, and may even engage with your emails, though it will never confirm opt-in. To know if you are hitting spam traps that impact your reputation:

  1. Monitor your bounces closely and check blocklists. If you are hitting traps at a network or mailbox provider, those providers may add you to their blocklist or reject your mail outright. Blocklist alerting will let you know if your IP or sending domain has been listed. You should also check bounce logs regularly to see if your emails are being rejected or blocked by any providers.

  2. Some mailbox providers manage their own spam trap networks and have a portal to view this data. An example is Microsoft whose SNDS tool allows senders to view spam trap hits on your IPs. This is only limited to traps that Microsoft has created themselves. Braze customers can access SNDS through the Deliverability Center.

  3. Utilize a third party deliverability monitoring service like Inbox Monster who owns or monitors an extensive spam trap network, and can share the number of traps your IPs or sending domains have hit. These services can also see the types of traps, the numbers of each type, and sometimes even the specific campaign that triggered the most trap hits.

Prevention and mitigation

Spam traps can make their way onto your list in many ways, but they all have the exact root cause of poor list hygiene and regular list cleaning.

To prevent spam traps from being added to your list, you can do the following:

  1. Verify email addresses using double opt-in to ensure new recipient addresses are both accurate and active.

  2. Do not purchase lists! Ever! In addition to violating most ESPs’ Acceptable Use Policies (including Braze’s Acceptable Use Policy), you should never send to addresses that haven't actively opted in to your specific brand. Aside from policy violation concerns, list vendors often scrape the internet for any addresses they can find to bulk up their lists. Scraped data may contain spam traps and other unsavory data, so avoid purchasing, borrowing, or renting a list even if it’s described as “opt-in”.

As for mitigation, the best way to suppress possible spam traps from your lists is to use engagement criteria on all sends. In addition to engagement being a critical metric that mailbox providers use to decide where to deliver an email (e.g. the inbox, the spam folder, or to reject the email completely), using engagement metrics such as “has opened” for your campaign sends minimizes the chances of spam traps also being included because a spam trap typically won’t engage with emails. That being said, trap operators like Spamhaus have shared that it is possible, if rare, for traps to engage with mail during their investigations.

It's essential for even legitimate marketers to have a mitigation plan ready to deploy in case of trap-triggered deliverability issues such as impactful blocklistings. If you suspect there are spam traps in your email list, the best action is to suppress them immediately. This will help to minimize the damage to your sender reputation and improve your chances of getting your emails delivered to your subscribers’ inboxes.

Remediation may require lots of segmentation planning; if there are indications that spam traps are on your list, apply strict filters. For example, send only to those who have opened or clicked in the last six months. You must also be prepared to decrease that time frame to three months, or even stricter, if trap hits persist. After you have identified the segment in which spam traps are likely to lurk, you can narrow it down further based on other criteria and send small sends to each segment until you believe you have identified the exact segment containing the spam traps. Once that segment has been refined, you will want to suppress those addresses, and determine if your list acquisition or management methods require additional improvements to reduce the presence of traps. In extreme cases, you may need to send a “permission pass” to your list, asking users to click a link to confirm their interest in remaining subscribed. Recipients who click can be retained, but those who do not confirm should be suppressed from further sends. Moving forward, double opt-in should be performed for all new signups. Traps are, after all, merely a symptom of problematic practices, not a diagnosis.

Key Takeaways

Spam traps are a critical aspect of email deliverability. They are created and maintained to catch spam, which may be malicious or simply misdirected marketing mail. Sending emails to spam traps is an indication of poor list hygiene practices such as scraping the web to grow the subscriber list, purchasing lists, infrequent list hygiene, or a lack of proper consent being obtained prior to sending emails. Sending to spam traps can significantly harm your sender reputation and email deliverability, and cause emails to be filtered as spam.

To avoid hitting traps, ensure you maintain a clean email subscriber list by regularly removing any inactive or bouncing email addresses. Always gain proper consent from users before adding them to your email list using methods such as double opt-in / confirmed opt-in and monitor results closely. Lastly, do not purchase, trade, or share any email lists, even if a trusted partner offers it to you for free. It’s just not worth the risk.

Interested in learning more about how Braze can guide and support you achieving stronger email deliverability? Check out our guide to Demystifying Email Deliverability.

Pooja Raje and Dan Stone

Pooja Raje and Dan Stone

Pooja Raje is a Email Deliverability Principal I at Braze and Dan Stone is a Team Lead, Email Deliverability at Braze.

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