Email List Hygiene

Email Validation 102: Pros and Cons

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We’re back with our next blog in our partnership with Lauren Meyer, Mailjet’s global VP of delivery & head of operations, North America. What are the things you should expect to encounter, positive and negative, when you start cleaning your email marketing lists via validation?

Considerations for the Marketer

If you checked out “Email Validation 101: What is it and why should I care?,” we covered the ins and outs of email list validation—what it does and doesn’t do—and along the way, addressed common myths and misconceptions. And if you did, congratulations; you’re a bona fide validation expert ready to look at choosing the right vendors for the job. But before you do, let’s take a look at some trends and features to be considered before you make the leap.

Consideration #1: You might want to work with multiple vendors

As we’ve pointed out, not all list validation vendors are created equal, and you might want to work with multiple. According to The Relevancy Group’s report, “The Power of Email Verification and Multi-Method Hygiene,” marketers using multiple list hygiene methods (often provided by more than one vendor) outperform those that do not. While we don’t shy away from recommending multiple vendors to our customers, there’s an important underlying consideration: Are you paying for the same results twice or more?

In a benchmark we conducted while building our own email validation tool, we found many offerings in the industry are using the same underlying technology. Or more simply, Vendor A is actually using the backend of Vendor B. Validation providers reselling their technology to direct competitors is a very common practice, so before you make a purchase, it’s worth asking your prospective service provider: Is your technology proprietary, or are you reselling someone else’s?

Consideration #2: Your results may vary

Most list validation solutions hinge on checking addresses against SMTP. Without getting overly technical, SMTP-based checks are conducted when a vendor takes your address, runs some small checks to make sure it’s valid syntax, then opens a connection to a receiving mailbox provider to see if it returns an error.

This type of validation is highly subject to inaccuracy because on average 16% of lists uploaded into our system are accept-all addresses, meaning they can’t be validated via SMTP. We’ve seen that percentage as high as 30% on individual lists. As we mentioned earlier, not all vendors are created equal; some are opening SMTP connections using poor practices that result in outright blocking at most major providers. How can someone validate an address if they’re blocked?

Psst: They can’t.

It’s also worth considering mailbox providers like Verizon Media Group (AOL, Yahoo) configure all of their mailboxes to be accept-all. This means that no matter what address they attempt to reach, a valid SMTP response is received and as a result, a substantial portion of your list could contain bad addresses while being flagged as valid. When you’re evaluating vendors, we recommend asking what steps they take in addition to SMTP to account for accept-all addresses, spam traps, etc., so you’re not frequently paying for false positives or false negatives.

Consideration #3: Which features best suit your needs

Email validation solutions have largely operated the same over the years, and we think there’s significant room for improvement. If you’re simply wanting to clean lists after collection as a means of purging bad data, the status quo may work for you. However, as we’ll outline below, list validation can lead to both a false sense of list quality and reliance on validation to account for problematic list growth practices.

When considering a vendor, just ask them for their track record. What new features have they released in the past 6-12 months? What does their platform offer beyond post-collection address disposal? With the right mix of analytics and features to improve address collection at the source, validation can become a marketing enablement activity instead of the traditional risk-reduction model. If the goal is to send to more valid addresses, and we’re now aware of accuracy concerns, what can list validation solutions offer YOU to support valid, positive list growth?
If you’re feeling ready to dive in, let’s look at some of the pros and cons of email validation from a deliverability perspective. Take it away, Lauren!

Pros and Cons for Deliverability


  • Reduce your hard bounce rates
    By removing at least some (if not all) invalid email addresses, you will reduce a lot of your hard bounces, which will help improve your overall deliverability.
  • Reduce your spam complaint rate
    While the traditional benefit of email verification is to remove invalid addresses, your efforts can also have a positive impact on your spam complaint rates, particularly for role addresses (e.g., admin@, sales@, etc). These addresses are often shared by multiple recipients, and while one of them may have subscribed to your mailing list, someone else receiving your emails may report them as spam. Most validation tools filter out role addresses from your mailing list, so if you choose to suppress them from future mailings, you’ll likely be saving yourself some pain in the complaints department.
  • Save your most precious asset…time
    Maintaining a clean list between campaigns can be time-consuming, and so can working with ISPs and anti-spam services to resolve blacklisting issues caused by poor data quality. If you’re using an ESP, recurring high hard bounce rate could lead to sending restrictions and eventually even closure of your account. Removing hard bounces from your list prior to sending can ensure you’re able to focus your energy on more important things, like creating content your recipients will love.
  • Increase your campaigns overall ROI
    Improving your data quality will have a positive effect on your deliverability, which means more recipients seeing your emails in their inbox and higher engagement with your brand.
  • A better understanding of the email addresses on your list
    By verifying your list, you may highlight improvements needed in your email collection and list management practices. For example, if you notice a high presence of typo addresses on your list, you may want to implement a double opt-in process or real-time verification tool as part of your signup process.
  • Reduction operating costs for your email program
    Most ESPs charge based on email volume, so by removing inactive addresses, you will also reduce your overall volume sent. Less cost, more impact! ?
  • Increase the quantity and quality of prospects
    Many companies now offer real-time email verification services, which can help you achieve a higher level of accuracy right at the moment when someone enters their email address in your subscription form. More valid email addresses on your list translate to a greater number of revenue opportunities, and also ensures you’re primed to avoid deliverability issues before they start!


  • A false sense of confidence in the quality of your “cleaner” list
    This can lead to overly aggressive mailing practices, resulting in a negative reaction from recipients such as higher unsubscribe and spam rates. Thankfully, you can control this…don’t let list validation be an excuse for poor sending practices.
  • Relying too heavily on list validation tools to clean up problematic lists
    This can mean some marketers engage in overly aggressive list collection practices, which increase the risks for deliverability. List validation is there to polish your quality lists, not to turn a pebble into gold.
  • Cost
    Quality list validation services are not free and can become expensive at scale. In addition to the actual cost for email validation, you’ll need to also account for the time spent choosing a provider and actually validating your lists.

That’s all for now! We’ll see you again in two weeks. Until next time.

Author: Lauren Meyer

Lauren is responsible for Mailjet’s global deliverability and compliance, and also directs Mailjet’s North American operations. She is a data nerd at heart, who is passionate about spreadsheets and spends much of her free time juggling twins and searching for her next great slice of NYC pizza.