Email List Hygiene

Email Validation 103: What questions should you ask vendors?

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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. This time, Lauren and Alex give you the right questions to ask when you’ve finally decided to take the plunge on email list validation.

Before we begin, it’s important to consider why you’re interested in list validation in the first place, since this will shape the list of pros and cons you use to compare vendors. Some questions you can ask yourself include:

  1. What issues am I trying to solve (or prevent)? The answer to this will help you determine if you should focus on solutions that offer real-time address validation, batch method, or both.
  2. How much data do I want about my list? Having access to granular data of different email addresses can absolutely help with your investigation and identifying the next steps. However, there is such a thing as too much info. What data will you actually use to inform decisions and which are simply “nice to have”?
  3. Is the service going to be used for my business or my clients? Are you looking to validate lists from your own contact list, or perhaps as an agency or SaaS tool like a CRM, are you looking for a solution for your clients who all manage separate contact lists, collected through a variety of methods?
  4. Am I looking for an ongoing validation solution or a one-time review of my contact list? One-time reviews could be for tasks like sending a re-engagement campaign to recipients you have not contacted recently (e.g., more than 6 months), following the advice of your ESP after a compliance issue, or simply trying to clean your list of typos and other hard bounces. On the other hand, ongoing validation is great for ensuring new signups or users are in fact real addresses—this is the kind of validation for which we at 250ok strongly advocate.
  5. What is my budget? Perhaps you think this should have been the first question. Price is certainly an important consideration, as validation services vary greatly in quality and cost, but more important than anything else is ensuring the solution you select meets your core needs.


Now to the meat of things. Based on our experience at Mailjet and my personal experience with email validation tools across the industry, here are some questions to ask potential vendors when evaluating email validation services:

  1. Are you GDPR-compliant? You can expect to see this question or some variation of it more and more in RFPs and other vendor selection surveys. Data protection, especially when it comes to email and other personal contact info, is an increasingly important consideration. Some benefits of a GDPR-compliant vendor (or other legislation like CCPA) can include an option to only verify email lists on EU servers, access to details regarding a contact’s country of origin in the verification report, and an easy process for requesting details about (or deletion of) the data the company has on you.
  2. What methodology is used to validate my contact list? There are many ways a vendor can check if the addresses on your list are valid, each with varying quality and rigor. As we mentioned in Validation 102, your results will vary from provider to provider, but here are some topics to consider discussing with your vendor:
    • Given that most lists are comprised of 15-30% Verizon addresses (AOL, Yahoo), how do you classify accept-all addresses?
    • Do accept-all addresses often inflate the valid/deliverable counts? Are you using some form of caching or third-party data to determine which catch-all domains and addresses are actually real people?
    • Do you believe direct opt-in should supersede do-not-contact lists? Will you suppress or discard my valid addresses that appear on do-not-contact lists such as the DMA’s list?
    • In your terms of service, will my list validation results be subject to reuse or be used to enhance the lists of your other clients? If so, can I opt out of this process to meet compliance needs?
    • How do you identify typos, misspelled addresses, or invalid address syntax without a significant number of false positives?
    • If addresses are classified as “unknown” or “unverifiable,” do you stop processing the address or do you have retry logic in place to make sure it’s not an intermittent connection issue or blockage?
  3. What kinds of tools do you offer? Many vendors offer the ability to set up real-time verification using API, as well as run batch validations via a CSV upload or an API call. Some vendors may even offer integrations with your email service provider (ESP), which can make validation a seamless step within your email program. Services like email deduplication, syntax, and domain verification are quite common. Other vendors also offer spam trap removal or the ability to flag addresses on your list with a higher likelihood of marking your mail as spam. As a reminder: be wary of any vendor who claims to be able to remove 100% of the spam traps from your list. This is simply not a reasonable promise.
  4. How many email verification categories does your service have, and what are they? Depending on your list validation goals, you might find it valuable to have your list broken down into several categories based on risk. Many deliverability issues stem from issues with data quality, so this additional granularity can be helpful in understanding how to optimize your list collection and maintenance practices.
  5. What kind of support do you provide for the results? If you use an ESP, their deliverability team may be willing to provide guidance or analysis on the results of your list validation (Shameless plug: that’s what we at Mailjet offer!). If not, you may want to inquire about consulting services available to help you understand how to interpret your results, highlight portions of your list which pose elevated risks, and create an action plan for improving your list collection and maintenance practices. This kind of analysis can be incredibly helpful in optimizing your deliverability and ROI with email.
  6. What is your accuracy rate and do you offer a guarantee? In other words, when email addresses are verified using their service, can you guarantee that those addresses will not bounce? Most vendors guarantee a deliverability rate between 95-99%. If they are offering any kind of quality guarantee, it’s a good idea to find out what kind of recourse you can expect if the results are not what was promised. Will they refund your payment? Will they assist you with blacklist mitigation and deliverability assistance? If not, you may want to consider the value that their guarantee brings.
  7. Am I able to run an accuracy test on a sample file? We all know marketing teams can make pretty much anything sound great, and any guarantee of quality may not be worth much more than the pixel they’re printed on. Having an opportunity to test their service on a small portion of your list allows you to determine if the validation process and results are simple to understand. This can also provide enough granularity for you to have actionable insights.

One last reminder: Validation is not meant to be a safeguard for when you want to purchase a list of email addresses without recipient consent. This process should be used over time on an ongoing basis to further ensure the validity of your active mailing lists you’ve built using ethical and appropriate methods. 250ok is a strong proponent of this philosophy, which is why we only sell our validation service to full-suite customers, as it’s simply another piece to a large and multi-faced email marketing puzzle.

Anyway…Thanks for stopping by for another blog in our Validation series! We think we have maybe one more in us…

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.