Have you ever received a "bounced" email?

If you send cold emails, you probably have. If not, I salute you! 🍻

The reality of the situation is... you get a few "bounces" first. Then, one day you'll see that your campaign results are becoming worse and worse. Game over comes after that when your emails start landing in SPAM. 😳

This is what happens when you don't verify your prospects' email addresses before sending them a campaign.

But, there's a better way to do it. I'll show you how to react to a bad bounce rate, protect your email reputation, and make sure your emails never end up in spam.

I've tested 7 top email validation tools in order to identify which was is the best. Full analysis and all the numbers... and I'm gonna show you everything.

What is bounce rate in email outreach?

When it comes to cold email outreach, there are a few metrics you ought to keep an eye on - open, click, and reply rates. These are the good ones that show your emails are generating engagement.

But there's another category. I call it the "dark side" of your email campaign. Besides the bounce rate, this is the place where you'll find the unsubscribe rate and, if you're a lemlister, the not-interested rate.

Now, the bounce rate is the % of emails that get sent back to you. If the email can't reach the recipient, it gets returned to you with a notification of its status.

what is bounce rate

What is the difference between a hard and soft email bounce?

There are 2 types of bounces: soft and hard.

Soft bounces are temporary delivery failures and can occur for a variety of reasons. There may be a temporary issue with the receiving server, your emails might be too big, or just some issues on the receiver's side like a full inbox for example.

Hard bounces are permanent delivery failures. This could be as a result of an invalid email address, an outdated domain, or an address that has fallen out of use, and in the worst-case scenario become a spam trap.

hard bounce rate

The "soft" bounce isn't a big deal, but the "hard" bounce is. This has short- and long-term consequences on the outcome of your campaign.

If your cold email bounces, it means that this specific lead won't get any emails from you.

So you spent your time and money on preparing audience profiles, finding their emails, and sending everything, but some people don't receive anything.

Not fine.

However, the long-term threat is even more severe.

Sending thousands of emails to people you haven't done any research or email checks for. As a result, the campaign is sent to invalid addresses.

This is a huge trigger for Google and any other email provider. If you do what spammers do, you have a huge chance to lose your email reputation.

So if you don't verify email addresses, it leads to problems with email deliverability. You have a higher chance to be trapped by SPAM folder.

what is bounce rate

Bottom line?

"Hard" bounce rate plays a huge role in the likelihood of you being trapped by SPAM filters.

How does email verification work so you can verify email address without sending email?

There is a solution to avoid bounces - use an email verification tool such as the Bouncer email verification software.

There are lots of different algorithms and apps that do that, but only 3 main types of verification they all perform:

  • Syntax check

It checks whether an email address is spelled correctly - has no spaces, commas, and if all the @s, dots, and domain extensions are in the right place.

  • Domain check

It checks the domain and email address on it making sure it works properly.

  • Email ping

Email verification tools send messages to a receiver's server to confirm whether the email address actually exists on the server and if it is active.

So now we know how email verification tools work. But the real question is my friend... what is the best tool?

... bringing me to my experiment!

Searching for the best email verification tool

I took 7 most popular email verification tools that sales reps use.

These sales reps are members of the biggest closed community for salespeople - lemlist family, and they've voiced their opinion:

Here's the setup of my experiment.

I took 1k email addresses, knowing that 800 of them were correct and 200 weren't. In other words, the result that the tool needs to give me is that exactly 80% of my emails are valid in the list.

How did I add "incorrect" emails?

If we have emails like "[email protected]" there won't be any sense in making such an experiment, since every validation tool can detect that.

So we just took correct emails and added extra letters or numbers, so it looks ok. But they're still incorrect emails. Devious, right? 😈

By the way, if you know an email verification tool that wasn't used in this experiment, ping me on LinkedIn.

The formula I was using to evaluate the results:

  • Validated correct emails among correct, e.g. 750/800=93% (the higher the better)
  • Found wrong emails among wrong emails, for example 20/200=10% (the higher the better)
  • Total results: 770 emails (bounce rate 2.5% which is good and 50 lost people)


The price for 5k contact is $25, the free trial lasts for 100 contacts:


The price for 5k contact is $13, the free trial is 1000 contacts:


The price for 5k contact is $40, the free trial is 1000 contacts


The price for 5k contact is $25, the free trial is 250 contacts:


The price for 5k contact is $10, the free trial is 100 contacts:


The price for 5k contact is $29, the free trial is 1000 contacts:


The price for 5k contact is $39, the free trial is 100 contacts:


The price for 5k contact is $10, the free trial is 100 contacts:

Here are the experiment results

All tools verified 1k contacts quite fast, taking them between 5 and 10 minutes.

Except for Debounce... this one took more than 2 hours. 😫 This is the exact time from the stopwatch:

The majority of them have a pretty nice design (especially Truemail, Thechecker and Blazerify)

But we are here to find the tool that will help us avoid SPAM folders!

And all tools are pretty great in finding "wrong emails"! No matter what tool do you use, your bounce rate will be low (less than 1%).

But, since I took only "green"/valid/safe-to-send results and didn't count "catch-all", there is a huge difference in finding valid emails among correct emails. For example, if you use Clearout, you'll send 768 emails. If you use Thecheker it'll be 598.

The difference is 170 valid emails!

Choose what tools works for you and always keep your bounce rate low like I have:

Wrapping up

Now we know all the aspects of "bounce" rate.

And what is more important, we also tested and found the best email verification tool!


With ❤️ to your Growth,

Ilya from lemlist