Picture this: you’ve warmed up your email domain and configured your DNS settings. Your copy is excellent, full of personalization, and free of SPAM-triggering words. The first batch of marketing messages goes out…and a lot of them come back as undeliverable. There were two critical steps missing in your process: testing email deliverability and verifying the email addresses.

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If you don’t verify email addresses before sending campaigns, you might be wasting time messaging accounts that don’t exist. Your prospect may have changed domains, had a typo or entered a false address just to get a download. Checking email deliverability in advance can help you avoid this scenario and protect your domain reputation in the process.

What Is Email Verification?

If you don’t verify the email addresses before sending email marketing campaigns, you might be wasting time messaging email accounts that don’t exist. Your prospect may have changed domains, had a typo, or entered a false address just to get a download. Sending messages to invalid email addresses decreases your reputation online and can affect deliverability lowering its rates. If you verify their email addresses in advance, it can help you avoid this scenario and protect your domain reputation in the process.

Why Should You Verify Emails?

It’s a fact of life that occasionally, an email will bounce or be undeliverable. Two types of bounces can occur:

  • Soft bounces, which are due to temporary problems like a recipient’s full inbox. It’s often worth trying to send the email again in a few days; you may be able to reach your prospect after the issue is resolved.
  • Hard bounces, which are due to permanent problems such as the account not existing. It’s impossible to reach your contact at this email address, and you should stop trying.

However, a single bounce here and there isn’t a problem. When your marketing emails regularly bounce, you:

  • Miss the chance to connect with a real prospect
  • Lose time you can’t get back
  • Tarnish your domain reputation — particularly in the case of hard bounces.

High volumes of hard bounces can be so damaging that your domain or IP may land on a blacklist, which tells ESPs to flag all your messages as SPAM. You won’t be able to reach anyone easily, valid email addresses or not.

Regular email verification reduces the chances of this happening.

How Email Verification Works

You can verify new email contacts before you send them a message. This way, you can clear any unverified addresses from your list and remove hard bounces that may affect deliverability

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It is a simple process when you know how to test email deliverability. Choose an email verification tool, provide your prospects’ addresses, and get the confirmation as to which ones are valid. Problem solved — and your sender reputation saved.

Email verification tools perform a variety of syntax, domain, and spam checks on the emails you’re providing to validate, if they’re still active, or if there are any other email deliverability issues with the inbox placement you’re hoping to reach. The main email verifier workflow looks something like this:

Step 1 – Syntax check – the core feature of email verifiers where the spelling of email addresses is checked while also making sure there are no missing or special characters in the specified address.

Step 2 – Domain check – This is where the email deliverability tool checks whether the domain of the email address actually exists, is registered, and is working properly.

Step 3 – Email ping – this step is a bit more technical than the first two. It’s the technical process of the verification service pinging the email address with an HELO message, then awaiting the response from the email servers. This is basically a message indicating the intent to send a message to the recipient’s server. This is the usual workflow when sending emails: a connection is made, after which the actual email is sent. In this process, the step of actually sending an email is left out while still receiving the needed response from the recipient’s email server. Based on the response this mail server will bring back to the email verification tool, it will either classify the email as “deliverable,” “non-deliverable,” or “risky.”

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Different email validation services can provide you with all or just some of these verification methods.

When to Test Email Deliverability

There are various factors tagging whether your email will land in the receiver’s inbox or spam folder. Email Deliverability is basically the email placement. What are the cases you need to test it?

  1. Before your cold email campaign
  2. During your cold email campaign

The first case, that is before your cold email campaign, is when you need to test if the campaign is automated. The second one is required only if you presume low email deliverability, get blocked, or land in the spam folder too much, so you need to increase your sender reputation and conduct regular spam checks. Your sender’s score depends on many factors, so make sure to engage in email deliverability testing as a part of each campaign.  

Based on this, there are a few types of email deliverability tests:

  • authentication (the proper configuration of the outgoing email server)
  • content spam checkers (it is a spam check of the content – checking whether the message will be caught by spam traps by email service providers due to spam-triggering words)
  • email deliverability test (comprehensive deliverability reports on delivery rates)
  • seed list (to check out what will happen to the emails you send to various subscribers who use different inbox providers, ISPs, browsers, and devices)

All of these methods to easily test email deliverability can hook any email deliverability and spam issues at an early stage, so you are able to react on time.

Tools to Test Email Deliverability

Make email verification a regular part of updating and cleansing your contact lists. Moreover, check up on your email deliverability rates. It’s simple to test email address deliverability with these tools:

SendForensics is a perfect option if you are looking for comprehensive deliverability reports on email deliverability. Moreover, it conducts comparisons with other companies, so you can always see what you have to improve for a better sender reputation.


  • A free tool – if you have an individual account, this version is free (in the case of a single sending domain)
  • You get optimization features before sending and measurements afterward.


  • In some cases, the recommendations contradict each other. 


GlockApps is an excellent choice. Once you know your email addresses are valid, you can use this online tool to assess the overall email deliverability of your outbound email addresses. This service helps you identify any problems with your email content, check blacklist status, determine if a particular ESP is blocking your email messages, and more.


  • Very consistent and easy to use
  • An easy way to improve email deliverability due to detailed reports


  • Inadequately documented API
  • Double opt-in confirmation emails are complicated to test


Tools for email verification:

MailTester offers flexible pay-by-the-email pricing or recurring subscriptions, with rates as low as $0.001 per email. Verify single emails as you get them, or scan your whole list regularly.


  • Perfect response time by customer service
  • Paid plans are supported by JSON API
  • Efficient email spam checker


  • The free version only allows checking spam scores.
  • The historic data of your tests is stored only for 7 days and then gets removed for free users.


Clearout also offers credit-based and subscription plans to suit large and small businesses alike. You can get 100 free credits on signup to try the program out — that’s enough to test 100 emails.


  • Accurate email validation
  • Cost-efficient 
  • User-friendly and easy-to-navigate


  • Not enough integrations and third-party services
  • The long validation process of large mailing lists


Bouncer also offers a price-per-email rate and 100 free credits to test the service. Paid plans start at only $0.005 per email. The more emails you test, the cheaper it gets.


  • Accurate email verification 
  • Highly professional customer support
  • A large selection of subscription plans


  • A free plan provides only basic information
  • Poor accuracy of email verifications 


Mailgenius. is another email testing tool that aims at checking your emails reputation and content in general. This tool provides you with useful pieces of advice to help you emails reach the inbox.


  • You get instant feedback on the reasons your emails end up in the spam folder
  • Adapted to all email providers
  • Custom solutions


  • Features are rather basic and simple
  • Pricing for paid plans


Warmbots is a great tool for improving your deliverability. Once you connect your email account(s) to Warmbots, it starts exchanging dummy messages with other Warmbots users. The messages get automatically replied to, taken out of SPAM, marked with high importance – it all helps you build a strong reputation as a sender.


  • imitates human-like behavior to build strong reputation
  • provides you with accurate and up-to-date SPAM rates
  • it’s free if you’re warming up no more than 3 email accounts


  • you need to create filters in your inboxes so that you’re not flooded with warm-up messages 
  • you can connect only emails with working IMAP and SMTP


You can start with a professional, free email deliverability tool. And remember – sending quality content to well-targeted prospects is not SPAM, and should not be treated as SPAM. We follow this principle here at Growbots, that’s why we decided to offer such a solution.

Take your cold mailing to a whole new level. 

Try it out yourself!


What if I Suspect My Domain Is Already Blacklisted?

If you’ve already had a lot of hard bounces or your email campaigns are performing poorly, you can check to see if your domain or IP addresses are blocklisted. It’s often possible to conduct an email deliverability check directly with a blacklist, like Spamhaus, or use other email deliverability testing tools like Mailgenius, GlockApps and MX Toolbox.

Blacklists have different steps to request removal. If a blacklist has damaged your domain or IP reputation, you may benefit from going through an email warmup process again. 

Not blacklisted and still having trouble? You may need to take some tactical anti-SPAM measures that can help with avoiding spam filters and improving email deliverability.

How to Collect Verified Email Addresses

When running email verification tests, you should find that most of your prospects’ email addresses are real and valid. If you’re seeing the opposite result — long lists of invalid email addresses — it’s time to rethink how and where you are collecting these leads.

  • If you’re offering a downloadable lead magnet, make sure email entry is a required field on the form and that the lead magnet is emailed to the prospect, rather than allowing them to download it directly from your website after entering their information. This encourages website visitors to use their real email addresses.
  • Similarly, when collecting leads on your website, make sure your form is structured so that the email address field type is set to email, not text. This may help reduce but not fully eliminate the chances of someone typing in a fake email address or string of numbers.
  • Don’t purchase bulk email lists from questionable data brokers. If you partner with an email service provider, make sure they’re a reputable source and take their own steps to verify emails.
  • Contact new leads in a timely fashion. The longer you wait to reach out, the larger the chance that some of your leads may have changed email addresses or companies.


Ultimately, the best solution is to use a prospecting tool. Growbots makes your experience easier and faster by finding real users and verified email leads that fit your ideal customer profile. We take care of our clients who can monitor their deliverability within our app and improve their deliverability within the app. Plus, every Growbots account includes built-in GlockApps email testing and a world-class Customer Support or even assistance from our Strategy Consultants to help you on your outbound campaigns (go and see pricing plans). 

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Chris Zawisza

Chris Zawisza

Head of Sales @ Growbots - laser-focused on the growth of Growbots’ customer base. Always eager to brainstorm and explore new ideas.