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How to Verify Email Addresses: The Definitive Guide for 2023

Apr 16, 2020

If you’re struggling with email deliverability, high bounce rates, and poor conversions, there could be one simple reason – you’re not sending them to the right email addresses. And we don’t mean the wrong target audience. Your emails could simply be bad – and they need to be verified.

How to verify email addresses? by Bouncer

Email verification is the process of checking your email lists to make sure those addresses are legitimate, active, and free of typos and errors. Of course, doing this manually is out of the question.

Today, we’re going to show you what email verification is and how to verify email addresses the easy way.

8 reasons for verifying email addresses

Many email marketers think that there is no need for an active email verification process. They assume that they can periodically clean up their lists based on bounces or even just leave them as is.

After all, they wonder, what harm is a bad email address doing? The reality is that email verification can greatly benefit your email marketing campaigns and give you a better email deliverability rate. These are a few benefits of email verification:

Increasing your deliverability

Verified email addresses are more likely to be delivered because you can be certain that they are valid.

Why spend time crafting the ideal email only to send it to dozens, hundreds, or thousands of bad email addresses?

how to verify email addresses?


When you check email addresses, you ensure that your messages are likely to be received.

Avoiding hard bounces

An undelivered email is more than just a waste of time.

It will also frequently result in a hard bounce. These are error messages sent by the recipient’s email server to let you know that something went wrong.

email bounce types


If you get too many hard bounces from an email server, it may start filtering all your messages to spam. If you see an increase in bounce rate, it could be just that you have too many outdated emails. A quick verification can help you get to an acceptable bounce rate easily.

You’ll also be able to avoid spam traps, email addresses created specifically to prevent spammers from reaching people’s inboxes with advanced email sending schemes.

Maintaining sender reputation

Email servers aren’t the only ones looking for bad emails.

Email service providers are also checking your bounce rate. If they see that you are sending too many emails to bad addresses, they may blacklist you. This can have even further-reaching implications than spam filtering.

You may find more and more of your emails bouncing, even if they are sent to valid addresses on your contact list.

Checking for catch-all emails

Some email servers use catch-all addresses, accepting all the emails that aren’t sent to valid email addresses at that business domain.

There are two problems with this.

First, a catch-all may send a hard bounce even though the email is received.

Second, chances are good that no one is actively reading the email received by the catch-all.

Getting clearer email campaign metrics

Beyond the damage to your email delivery rate, bad email addresses can also cause misleading email campaign metrics.

You may see an abysmally low open rate and click-through rate, for example.

However, this may simply be because half of your list is made up of unverified emails.

Saving money

When you store and send to email addresses, you are incurring costs of both time and IT resources.

While a handful of bad email addresses won’t have an impact, if you have a major problem, you could be wasting significant money.

Cleaning up your mailing lists is good for your bottom line.

Purging temporary or deleted addresses

An email address does not need to be bad to be a problem.

Many people create temporary addresses to sign up for things or delete their older addresses. A disposable email address works for a short period of time, after which it is gone for good. People use these when they don’t want their primary email address to be associated with a new account on some website.

In either case, emails that once worked may stop suddenly.

Actively cleaning your list will get rid of every temporary address on your bulk email list.

Finding typos

You may have bad email addresses in your list that are simply typos. For example, [email protected] may be written as [email protected] (the “m” switched for an “n”).

A rigorous email verification process can find these typos and weed out every invalid email address. You can then correct them and deliver your email as intended.

With the right toolset, it is easy and time-efficient to check email addresses. With so many benefits, there is little reason not to implement an email verification strategy.

When to verify and check email addresses

You don’t need to verify your email addresses excessively. It is valuable to verify email lists regularly. However, you only need to check if there has been a major change to your list or if you are struggling with poor metrics.

For example, you want to verify email addresses when they are added to your list. You also want to check email validity if your bounce rate exceeds 2% or your open rate is low.

In addition, it is a good idea to clean up your lists on a regular schedule. Consider checking roughly once per month. If you have a relatively small number of emails, you may be able to do this quarterly.

If you have very long lists that change a lot, you may need a more frequent schedule for your bulk email verification.

Please note that B2B lists need to be validated more often than B2C.

How to verify email addresses?

Email address verification is the process of checking to determine if an email address exists. When you are sending out emails, you want them to go to a real person instead of outdated or fake email addresses.

One of the best ways to ensure that they do so is to check email addresses on your list to ensure they are valid. 

Verification is a valuable tool in any email marketer’s belt. Deciding to validate the email addresses on your list, allows you to eliminate invalid addresses and disposable email addresses which results in improving your sender reputation and keeping your email account healthy.

Sending emails and managing bounces

Email validation is a simple way to improve your email campaign and in general your email marketing. The simplest way to verify an email address is to simply send a verification email to it. If you get a hard bounce, you can remove the email from your mailing list.

This is an inelegant solution. It can harm your email sender reputation, get you added to spam lists, and mess up your metrics as many emails will land in the junk folder. Sending test emails is better than continuing to email bad addresses. However, there are some better options.

Nonetheless, you should check your soft and hard bounces regularly. This is a great chance to clean up your list in between verifications and it’s crucial if you send a lot of cold emails.

Sending emails from another email address

Another approach is to send a test email from a dummy account. This is an extremely simple solution and moderately fast.
All you need to do is sign up a free account then send a test email.

Since it is from an alternative domain name, you can write almost anything in your email body. When you get hard bounce responses, you can remove them from your email list.

The main advantage of this approach is that it is very easy, even for tech novices. However, it is often inaccurate because you may not get clear responses and your messages could be filtered to spam folder.

Additionally, you will need to keep track of the responses yourself using a spreadsheet. For many email marketers, this is overly time-consuming and frustrating. Not to mention the fact that it is just bad to spam your recipients’ inboxes!

How to verify email addresses without sending an email

Verification of an email address without sending an actual email is possible, though is a complex process and may require some advanced techniques.

In this section, we’ll cover two alternative methods: creating your own solution and using an email verification service such as Bouncer.

Check the email syntax

The first step in identifying invalid email addresses is to validate the email address syntax.

Valid email addresses consist of two parts: a local part (i.e. username) and a domain, separated by a “@” character and uses the following format: local_part@domain.

The local part may be a maximum of 64 characters long and can consist of:

  • uppercase and lowercase Latin letters A to Z a to z
  • digits to 9
  • special characters !#$%&’*+-/=?^_`{|}~
  • dot . , however, it should not be at the beginning or the end of the local part and it should not be next to another dot.

The domain may be maximum

  • uppercase and lowercase Latin letters A to Z a to z
  • digits to 9
  • hyphen , however, it should not be at the beginning or the end of the domain part
  • dot . , used to separate parts of domain labels (subdomains, main domain, and top-level domain)

One could describe those rules in a form of Regular Expression that would look as follows:



Ping the server

The next step in the process of email verification is to ping the mail server and ask it whether the address is valid.

This process is slow, cumbersome, and very risky for your infrastructure, as you can likely tell. However, it is quite accurate.

You need a tool such as Telnet on Windows or PuTTY or nc (netcat) on macOS.

Here are a few simple steps needed to verify an email address by pinging the email server:

  1. Look up the mail server using the command “nslookup -type=mx” followed by the email domain name.
    This should return several servers.
  2. Pick one of them and connect to it using Telnet.
    The command for this is on Windows is “telnet {mail server address} 25.
    The command for this is on MacOs is “nc {mail server address} 25.
  3. Then, say hi to the server by typing “EHLO {your domain name}”.
  4. Finally, it is time to check the email address. Start by typing “mail from:<{your email address}>”.
  5. Then, after the response code, type ”rcpt to:<{the email you are verifying}>”.

Here’s how the communication would look like for a deliverable email address:

220 mx.google.com ESMTP h3si7768221lfu.32 – gsmtp

EHLO mydomain.com

250 mx.google.com at your service

mail from:<[email protected]>

250 2.1.0 OK h3si7768221lfu.32 – gsmtp

rcpt to:<[email protected]>

250 2.1.5 OK h3si7768221lfu.32 – gsmtp


221 2.0.0 closing connection h3si7768221lfu.32 – gsmtp


And here’s what it would look like for an undeliverable address:

EHLO mydomain.com

250 mx.google.com at your service

mail from:<[email protected]>

250 2.1.0 OK l26si4867318ljg.18 – gsmtp

rcpt to:<[email protected]>

550-5.1.1 The email account that you tried to reach does not exist. Please try

550-5.1.1 double-checking the recipient’s email address for typos or

550-5.1.1 unnecessary spaces. Learn more at

550 5.1.1  https://support.google.com/mail/?p=NoSuchUser l26si4867318ljg.18 – gsmtp


221 2.0.0 closing connection l26si4867318ljg.18 – gsmtp


While proceeding with this method, a very important aspect is to properly recognize the responses of an email server. The important parts of the server SMTP response are so-called Basic status codes and Enhanced status codes.

Basic status and verification codes consist of 3 digits, where the first digit represents whether the response is:

  • 2 – positive
  • 3 – positive intermediate
  • 4 – transient negative
  • 5 – permanent negative

The second digit represents the category:

  • 0 – syntax
  • 1 – information
  • 2 – connections
  • 5 – mail system

Here are some common status and verification codes with their meaning:

  • 220 – connected – service ready
  • 221 – goodbye – service closing transmission
  • 250 – requested action OK and completed
  • 450 – requested action not taken – mailbox may be temporarily blocked for policy reasons
  • 500 – syntax error – command unrecognised
  • 503 – bad sequence of commands
  • 530 – authentication required
  • 550 – mailbox unavailable
  • 551 – user not local
  • 552 – exceeded storage

If you run cold email campaigns frequently, this method of bulk email verification can be quite lengthy and cumbersome.

Using an email verification tool

In many cases, the best way to verify email addresses without sending emails is to use an email verification tool. Email checkers are an especially popular option for regular email marketers and others used to send numerous emails.

The email verification tool automates the process to check email validity. All you need to do is provide your mailing list. There are a few benefits of using email checkers:

Accurate: Perhaps most importantly, email verification tools tend to be very accurate. You can be confident that your final mailing list only has valid addresses.

Speed: Compared to pinging the server, the tool-based approach is very fast. Plus, you don’t have to do any work to check email addresses. Just upload your list and let the system do the rest. Need to send thousands of cold emails at once? We have your back.

Support: Producers of verification tools like Bouncer know email marketing and verification. They can provide the support that you don’t get with other options.

GDPR Compliance (If You Choose Bouncer): While not every tool is GDPR compliant, Bouncer is! If you are doing business in the European Union, having a system that complies with these laws is important to protect your email sender reputation and save you from paying hefty fines.

Using a tool to verify email addresses is the fastest and simplest option. For busy digital marketers who send plenty of cold emails, this is a must-have.

email verification tool vs an in-house solution

Perks of using an email verification tool vs an in-house solution

Use Bouncer to verify email addresses in bulk

Email address verification is an essential part of a successful email marketing campaign. With Bouncer, you can bulk-check email addresses quickly and easily. Better yet, it is GDPR compliant.

Learn more about email list verification today. With this powerful feature, you can enjoy all the benefits listed above and more. It’s time to start verifying your email lists!

You go all the way here, so you are probably an email expert. If you are looking for new opportunities, you can check Jooble’s email specialist jobs near me.

If you want to verify email address validity, use Bouncer – the easiest to use, yet the most powerful email verification platform. Start your free account and try before you buy with 100 free credits! If you want to validate additional email addresses, paid plans start for as little as $8 per month!

Bouncer - email verification tool

Wrapping up

Email validation is necessary if you want to be successful in email marketing. Sending messages to deleted, misspelled or temporary emails is not only hurting your bottom line but will ruin your sender reputation. An email verifier tool can help you not only improve your email marketing metrics but also your overall profit.

Sign up for a free account of Bouncer today to find out how you can quickly and easily verify hundreds of thousands of emails. Just add your list of email addresses and we’ll show you which ones to remove with laser precision!

Frequently asked questions

What is the best way to verify an email address?

As outlined below, there are several ways that work. However, using online email validators such as Bouncer is the quickest and most efficient way. It lets you validate hundreds and thousands of emails quickly instead of doing any manual work.

Can email validation tools verify Gmail addresses?

The good ones can. With Bouncer, you can verify Gmail and deep catch-all emails, ensuring that your lists are free of temporary email addresses, outdated addresses and anything with a typo or an error.

Can I validate an email without sending any outbound emails?

You can with a tool like Bouncer. You don’t have to send a single email to do any verification – we’ll take care of everything for you.


Verify email addresses without
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