Three years ago I helped a small candle business from Jaipur prepare for their first big email campaign around Diwali. They had a list of 6,200 email addresses of subscribers that had signed up for the business over two years via their Instagram account, via a popup on their website, and via the offline events the business held. A lot of those paper cards must have had typos in them.
I started with a free email verifier. They are all over the web, and a free solution is often what a small business owner wants to spend first. So, we went with one of the most popular no-signup email verifiers. We would verify 100 addresses at a time, and the report would indicate about 91% of the emails on our list were valid.
It seemed like an adequate number of valid email addresses to send out a campaign of this nature. And send out a campaign we did. However, the resulting bounce rate of 8.14% would have gotten Gmail and Outlook to flag up for suspicious activity around the 5% mark. And indeed, the sending domain would suffer significantly from a poor deliverability rating – down to 3.19% for the next two campaigns I set up for them. Also, the open rate of 22.04% plummeted to a lowly 14.36%. Hard numbers to explain away to a very worried client.
After our email campaign was launched I started verifying emails of the list’s subscribers using paid email verifiers such as ZeroBounce, Bouncer or NeverBounce. The paid tools varied in the percentage of emails that were classified as valid, with 79% being the highest of all email verifiers I’ve tested including the free ones. Pingovo.com’s email verification tool is currently my go-to verification tool for new subscribers and it classifies about 79% of the emails on my list as being safe to send to. As I mentioned earlier, the 91% classification rate of the free email verifiers seemed way too good to be true, and in reality it was.
*Why the numbers don't match *
This led me to a realisation. Free email verifiers don’t do drastically different things to paid ones. They look at syntax, domain information and the existence of mailboxes. It’s the extent to which they test an email address and how often they test it that differs.
As an example of this, free email verifiers almost always mark catch-all domains as valid (i.e. they return a positive for the email address). This is because performing a deeper check to flag catch-all addresses as risky costs the free service money in server pings and in processing time. Paid email verification services on the other hand spend money on server pings and processing time in order to flag catch-all addresses as risky. It is their business model after all.
Greylisting. A topic usually best left to the forums on email deliverability. What I’ve found is that many free email verifiers will not retry a verification that has failed due to greylisting. Instead, they’ll mark the email address as invalid. This can be particularly problematic, as some free email verifiers will even make an educated guess as to the validity of an email address based on the domain alone. Paid email verification services, however, are designed to handle verification attempts that fail due to greylisting. Many of these services will include retry logic, and perform multiple verification attempts over a period of time.
*The spam trap issue nobody warns you about *
This was unknown to me, but apparently is very bad. I did work with a fitness coach a few years back that purchased an email list from a data broker for a candle business. Yes, candle business! The list was quite large but he wanted to reach out to people who had purchased candles online. I warned him of potential spam traps in the list but he didn’t listen. In the end, we did use a tool to verify an email list for him but not a free one. The tool we used, which was Kickbox at the time, flagged up 34 known spam traps in his list of around 6,000. We then removed these addresses from the list and the coach carried out his email campaign. Sending to just a few of these spam traps could have gotten his domain blacklisted from email providers such as Spamhaus and it would have taken months to get his sender reputation back to normal.
A free tool would never catch a spam trap address. Not because the free tool is worse than the paid tool, but because the data to identify spam trap addresses costs real money to license. Therefore, free email verifiers do not have access to spam trap databases.
*What the free tier is actually good for *
I should clarify that there are circumstances in which free email verification is completely sufficient. If you only need to verify a handful of email addresses – i.e., prior to sending a single cold email message – Hunter’s free tier for email verification or Mailtester.com will do just fine. Sure, there are daily limits of free verifications (25-150 depending on the tool), but for the occasional verification of email addresses for occasional cold emails, it’s simply not worth the cost of a paid subscription. For verification of rare use of contact forms on your website, same applies.
Another problem with free email checkers is that they are limited in terms of volume and often lack critical verification steps. In reality, a free email verification service is not going to cut it when you’re sending to thousands of people and your email sender reputation is very important. Most email verification services are priced per credit and then you can send as many emails as you want with that credit. For example, ZeroBounce costs $16 for 2,000 credits (which changes based on volume). So, for a list of under 10,000 emails, you’re looking at spending less than the cost of dinner at a nice restaurant to verify the emails and avoid potential problems with high bounce rates and email service provider account suspensions (which has happened to two of my clients in the past).
*The part people forget: time *
And then there's the time spent. All the time spent after a large email campaign to manually sort through all the engagement reports, to remove people who did not engage and then to warm up a domain that has not been used in a while by sending a series of smaller emails. The total time to get a sender reputation back to normal is usually around 2 weeks. I don't even want to begin to put a value on this type of time.
One thing I’ve noticed about free email verifiers is that they provide little to no additional information to help the user. Paid email verifiers, however, provide detailed information about the email address including: role-based email address, disposable email address, catch-all email address, spam trap, and more. Syntax errors are also found and reported. The information provided by paid email verifiers is invaluable and can help the user to understand where the sign-up form for their list may be failing.
*What I'd actually tell someone starting out *
Free tools are very good at checking the odd email before a cold send. However, for occasional use, the free tier limits (daily caps, etc.) soon become irritating. As I said above, for occasional use, paying for a subscription would not be cost effective. For larger lists, though, the cost of paid verification per email is very low, typically less than the cost of a nice dinner, and a small price to pay to avoid the problems described above. Remember that most paid tools charge by credit, not by subscription. For example, ZeroBounce charges $16 for 2,000 credits (as of the time of writing) which works out at $0.008 per email. If you have a list of less than 10,000 subscribers, the cost of paid verification is likely to be less than the cost of your email service provider suspending your account due to high complaint or bounce rates (as has happened to two clients of mine in the last few months).
As an aside, this small candle business has since then verified every single campaign with Pingovo and their current bounce rate is below 1% - for the cost of 2 candles per campaign.
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