How to Choose an Email Verification Tool: 7 Questions to Ask Before You Buy
It was an early Tuesday morning in 2022. Our email was flagged by a subscriber’s email account. I managed the email marketing for a small skincare startup that had imported a list of 18,000 contacts purchased online. We had added them straight to our Klaviyo email marketing platform without checking the list for quality first. By Thursday, the bounce rate had shot up to an alarming 12%. As of Friday, all our campaign emails were being routed to the Gmail subscribers’ spam folders. It took us 6 long weeks to slowly recover our sender’s reputation with a painstaking warm-up campaign. It cost the brand 3 months of steady email revenue in the end.
I was tasked to manage email marketing for a small skincare brand that had just imported a purchased list of about 18,000 contacts straight into Klaviyo. Nobody checked the list for quality before importing it into the email service provider’s system. Within four days the bounce rate had climbed to 12% and Gmail had started to send campaigns sent from the brand to the subscribers’ Gmail addresses to the spam folder. Six weeks were spent rebuilding sender reputation with a warm-up plan that involved sending smaller batches of emails on a regular basis. In total the setup had cost the brand three months of steady email revenue.
So here are the 7 things I ask before you give the guy your credit card details to sign up for an email verification tool for you and your clients.
1. Does it check more than just whether the email is formatted correctly?
The cheapest verification services only check for correct spelling of the email address (so they check for the '@' symbol and the domain name) and then call that verification. However, that is just spell checking, not verification.
Hunter (mentioned in our Workflows post for bounce tracking) has an extremely straightforward verification method that we verified on a 500 person test list of web attendees. On that list of 500 it marked 40 as “risky” to verify and a subsequent low volume test send confirmed 31 of those 40 to bounce for a very high catch rate. A less expensive (albeit re-branded) solution we tested verified the exact same list to be 98% valid for email verification services, and 8% bounced in real email sends a couple of days later. Not false, but also not checking very much.
Ask the vendor if their service performs SMTP-level verification (it actually connects to the email address’s mail server and attempts to verify if the mailbox actually exists). Don’t rely on the salesman’s word – if he starts rambling about how his service is the most advanced on the market and how he can verify emails within a split second, then you know he’s trying to avoid answering your question.
2. How does it handle catch-all domains?
This is one of the most common things that I have seen people get wrong when verifying email addresses.
A catch-all domain is a type of email address management for a domain, which automatically accepts all messages sent to any email address that belongs to that domain. Therefore, when checking an email address on a small company’s domain, even if the email address does not exist, the email server will usually confirm that the email address is valid. That’s why a verification service may flag an email address with a catch-all domain as being uncertain, meaning that even if the service confirms that the email address exists, it is not 100% certain that the email address is valid.
I usually see that a tool flags a catch-all domain with a label like “unverified” or “Catch-all detected”, but this does not necessarily mean that the tool is not responsible for the inaccuracy. I have seen tools like ZeroBounce flagging around 15% of the list as catch-all for a list of small business owners running their own B2B SaaS company’s domain. In contrast, NeverBounce reported only around 2-3% of the same list as catch-all for a different client of mine. However, the actual bounce rate for the campaign running on NeverBounce was higher than expected.
Also important: how does the provider classify catch-all addresses (as outlined above)? Will you be charged for these addresses even though the tool can’t verify them (i.e. confirm that they don’t exist)? Many providers charge the same for a verification of a catch-all address as for a verification of a valid address, which seems unfair given that the tool isn’t even sure whether the address does or doesn’t exist.
3. Can you actually trust the accuracy rate they advertise?
So another big question: How do you know how good it is? Every email validation service advertises 98% to 99% accuracy. It’s really meaningless. As I said before, that is based on testing on the list that they used to set the tool up. Which means that the list that was used to set up the tool could have been garbage.
Ask for the false-positive rate in the email verifier you’re testing. This will give you an idea of how often the tool misidentifies a good email address and flags it for a bounce. In my tests with Hunter’s email verifier, the false-positive rate for email addresses that were marked as “risky” was about 8%. I had the vendor explain the methodology behind this statistic, which I found to be very transparent. Other vendors would only repeat the same 99% number I’d already read on their website.
I’d like to see more detail about how a vendor is measuring the false-positives in their testing data, and have them explain in detail how they arrived at their advertised accuracy numbers. But asking for this detail should not be a dealbreaker.
4. Does it plug into the tools you're already using, without a workaround?
It's a minor detail. But believe me it's so much easier to do this and that when the apps connect to each other.
One e-commerce client using Klaviyo required a tool that had a clean integration with the email marketing platform. We were able to use Bouncer’s Klaviyo integration to verify emails in real time as users signed up for a newsletter on the client’s website. Another e-commerce client using HubSpot required a Debounce integration via Zapier, which was provided in a far more polished way than by the other email validation tools we looked at.
Another way to save a lot of time and effort is to check if the tool verifies email addresses in real time (i.e. as soon as someone submits a form) or in batches (i.e. after you’ve uploaded a list of addresses). The big difference between the two is that, with real time verification, you can stop bad addresses from ever entering your database in the first place. And that’s a very different workflow to the usual cleaning up a mess after it’s happened.
5. How is pricing actually structured, and do unused credits expire?
This is where I've seen clients get genuinely annoyed after the fact.
A lot of email verification tools sell their services in credits. Each credit can verify one email address. Therefore, it’s very important to check how long unused credits will expire. From my experience with such services, some of them can make unused credits expire even in 30 days. That’s why I was quite surprised when I found out that 4,000 of unused credits that I had bought for a nonprofit client in bulk a few months ago for verification of their donors’ email addresses expired as well. It all was buried in the fine print of the pricing page that I hadn’t read thoroughly.
Also worth noting: is a credit spent on an email that is deemed invalid or unknown, or only on an email that verifies to be a valid email address? As noted above, Emailable only charges for confirmed valid email addresses, which seems to me to be the more fair model of sender reputation verification services.
6. What happens to your list after you upload it to them?
It’s a simple point, but a key one to consider when looking at providers – especially when dealing with customer data subject to GDPR or similar regulations.
Many tools have a privacy policy that you should read. Some tools delete your list after a certain time of deletion (e.g. 30 days), others are silent on this point until you ask. Clearout’s support team were very good at answering this question for a European client of mine recently. They gave me a written time line for how long they keep lists uploaded by me for. That was very reassuring to read.
How long will the company keep your list for? This is another aspect of how a company will treat your data. Find out how long they will keep your list for after you have deleted it and write this down in your notes. Look for a company that will delete your list as quickly as possible and treat your data with respect.
7. Will they let you test it on your own messy list before you commit?
A smooth demo of a tool is always shown with example and very clean data. In reality you want to test the list with typos, old addresses, role accounts like sales@, admin@ and accounts that have not been emailed in the past 3 years.
The vast majority of providers now include a small free batch of emails (100-1000 free credits) in their demo sign-up to allow you to test the tool on your actual list, rather than a bland, perfectly-formed ‘demo list’. In the end, I ended up using the free trial on the old donor list for the nonprofit project mentioned above. This identified the instances of catch-all emails as well as role-based email addresses that were being flagged incorrectly.
I’d rather not commit to a service if they won’t allow for a free test (of any size) before purchasing credits. If they only allow for testing after you buy upfront then that’s a good indicator to look elsewhere.
The seven questions I laid out in this article are not difficult to ask. They don’t require a lot of technical knowledge and it’s worth the time to read through them before you purchase a sender reputation management tool. Each tool is going to work better for different businesses depending on factors like list size, how the list was built up, and what email service provider you’re sending from. But reading through these questions before you sign up for a tool is going to save you a lot of grief. As someone who spent a week of their life trying to fix a sender reputation that had somehow fallen apart, trust me on that.
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