The Complete Guide to Email Verification

Beginners Explanation to Email Verification
Thomas Roth Marketing Monkeys
Thomas Roth

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0 Comments16 minutes02.08.2021

Beginners Explanation to Email Verification

If you’ve ever had to work in email marketing, chances are you’ve had to deal with setting up new lists, migrating contacts over to a new email service provider, and consequently, a rise in bounce rates.

When businesses first begin growing their email list, they slowly gain emails into their database, and begin sending out content to these people via an Email Service Provider. But over time, bounce rate can become a huge problem for a lot of companies. The average bounce rate across industries is 0.7%, and if yours is drastically higher than this, then it is definitely something you need to look at.

Bounce rate is effectively the number of emails that are unable to be delivered. This could be for several reasons, as mentioned in this blog post. Irrespective of the cause, bounces can be prevented by means of email verification services.

What is Email Verification

Email Verification is the process of verifying the emails in your database. By proving that an email address belongs to a real person, this means they can receive and engage with your emails, without them being undelivered due to a soft- or hard-bounce.

In other words, email verification services help to ‘clean up’ your email database, so any invalid emails are removed before being flagged to your email service provider (ESP), which can tarnish your reputation and affect future email campaigns.

Why is Email Verification Important

If you have unverified emails in your database, your bounce rate, open rate, click through rate, and conversion rate could all be negatively affected. This is because emails either bounce or are sent to the user’s spam inbox. According to a study , having just 1% of “bad” (unverified) emails can reduce your deliverability by 10%.

Having unverified emails can happen for several reasons. On average, your email database will degrade by about 22.5% a year, due to people no longer using the email address that they signed up with. Additionally, Spam Traps are emails used to help expose businesses and marketers that add emails to their database without GDPR compliant permission from the user.

When you send emails to these addresses, you’ll begin to see your bounce rate increase, which could have a snowball effect on what is called your sender score. Your sender score (or sender reputation) is an indication of how reliable you are in sending emails, a poor sender score can mean your emails either enter the junk folders of your database, or don’t even reach them at all.

The three main factors which affect your sender score are:

  1. Bounce Rate: The percentage of emails sent that are undelivered
  2. Complaint Rate: The percentage of users that report your emails as spam
  3. Spam Trap Hit: The number of emails that are sent to fake email addresses, specifically designed to catch out non-compliant email senders.

So being able to verify the emails in your database can help you in two ways. Firstly, through opportunity costs. As we’ve discussed in previous blogs, email marketing has the highest ROI out of any marketing strategy. Every bounce means a missed opportunity at driving more revenue for your business.

As explained in our blog post on Email Bounces, there are two different types of email bounces: soft bounce and a hard bounce. A soft bounce simply means that the email address you attempted to send the email to is valid, but it bounces because of an issue outside of your control. Usually, this is because the recipient's mailbox is full, the email server was down, or your message was too large to be sent. A hard bounce means that there is a permanent reason that your email couldn't be delivered. This commonly occurs because either the attempted recipients email address does not exist, or because the recipient has blocked the delivery of your email.

Additionally, bounced emails impact your sender score, meaning you will soon see a lot of your emails be undelivered, and could even end up with your business being ‘blacklisted’ as spam or junk. This furthers your lost opportunity to drive extra revenue for your business, but also could have long-term complications for you.

Different ESPs and internet service providers (ISPs) have different thresholds for when they begin punishing your domain. For example, a complaint rate anywhere above 0.1% with AOL will see some of your messages sent to people's spam inbox. Simply put, the higher your bounce rate and complaint rate, the more emails will be sent to spam, and the more likely your domain is to be blocked from sending out emails. Sending just one email to a spam trap can result in your address being punished.

The consequences of having a poorly managed email database includes:

  • Opportunity cost
  • Decreased ROI
  • Damaged sender score
  • Potentiallly 'blacklisted' from ESP's
  • Poor customer experience

According to Tower Data, after implementing email verification, companies report over a 90% reduction in bounce rates, and a 20% increase in open rates. Depending on your business, these numbers can result in more sales, more brand exposure, and more customer engagement.

How Email Verification Works

Emails can be verified via using an email verification service (otherwise known as email validation, or email list cleaning). These services scan your entire database and check which emails are valid, and which ones aren’t, to help remove any issues before they are picked up by your email service provider, and negatively impact your sender score.
Email verification services use multiple steps to scan your entire database. These steps can differ, but the general steps are the same amongst all the good services.

1: Formatting & Syntax Check

Valid email addresses all have the same four parts:
  • Recipient Name
  • @ Symbol
  • Domain name
  • Top-level domain

This is what is known as the ‘syntax’ of emails. The recipient’s name is usually a specific person's name, a department, or a word such as ‘info’ or ‘support’. The recipient’s name must be under 64 characters, and can include a mixture of letters, numbers, and special characters (with some restrictions).

The domain name is the specific mailbox provider or website that controls the email address. This is usually a business domain name, or a service provider such as Gmail, Outlook, etc. Domain names are allowed to be up to 253 characters, and include a mix of letters, numbers, hyphens (-), and full stops (.)

The top-level domain is the part at the end of an email address, usually .com, .net, or .org. Different countries have different top-level domains, such as .ch for Switzerland, and for the UK.

If any emails in your database do not follow these formatting rules, then they are invalid, and will likely result in a hard bounce from your email campaigns.
Email verification services will scan your database and remove any email addresses that do not follow the required syntax.

2.Verifying Mailboxes

Some email verification services check the validation of different mailboxes, with different ISPs. For example, for the address, is Benjamin5 actually a working account at Google Mail?

Mailbox pinging is generally the most accurate way to find which mailboxes are valid, and which ones aren’t. Pinging simply involves pretending to send the mailbox a message, without actually doing so. In return, this allows your verification service to check if the email was undeliverable or not, without affecting your sender reputation.

Building pinging software can be a tricky thing and you should usually rely on some experienced software company such as Marketing Monkeys. Yes, you’ve got that right: We have built our own email verification software that’s been integrated with our Marketing Automation software called “Automation Monkey”.

3: Identifying Spam Traps

As previously mentioned, spam traps are emails used to help expose businesses and marketers that add emails to their database without GDPR compliant permission from the user. These email addresses have been created with the pure intention of punishing or blacklisting non-compliant senders.
Whilst these email addresses have good intentions, they can be extremely bad for your sender score.

If you’ve ever bought a list of people’s emails (which you shouldn’t!), there is a high chance that there will be some spam traps in that mixture of addresses. However, even if you have built your email list over years of hard effort, using the correct procedures, and being GDPR compliant, you still may have a couple spam traps that have managed to creep into your database.
If there are any spam traps in your database, an email verification service will remove it for you, before you end up getting blacklisted.

There are also bots which if in your database can increase your chances of your data being hacked. Using a good email service provider will make sure that the email addresses in your database are not only real emails, but also ones which won’t affect your bounce rate or complaint rate.

When Should You Use Email Verification

You can use email verification software at any time you like, but there are certain occasions where it is essential for you to do a full scan of your database.

New Contacts: The easiest and most effective way to keep bad emails away from your database? Validate them at the point of entry. Some email validation services should check for syntax errors, incorrect mailboxes, and spam traps as soon as a sign-up form has been completed.
This also gives you the opportunity to ask users to make corrections, in case they accidentally misspelt their email, which can result in an extra lead added to your database

High Bounce Rates: If you notice more of your emails are bouncing (not being delivered), it is definitely wise to run a verification of your database sooner rather than later as you don’t want this to affect your sender score.

Low Inbox Placement: If you’re measuring inbox placement, you’ll be able to see if the emails are landing in people’s primary inbox, or spam/junk folder. If you notice a lot of your emails ending up in people’s spam/junk, then it’s time to complete an email verification.

Re-engagment: If you haven’t contacted a list in your database in a while, then it may be worth it to verify this list beforehand, so you don’t send any emails to invalid addresses or spam traps.

A Quick Note About Catch-all Policies

Most businesses or email senders use a verification tool, achieving all of the above, and then get stuck at a point where they ask if a mail server or domain has catch-all policy enabled or not.

A catch-all address is designed to ‘catch’ all emails sent to an unverified, non-existing email address. For example, if the Marketing Monkeys server was set up as catch-all, then any emails sent to the domain would be accepted, even if the recipient name doesn’t exist, such as These emails can damage your deliverability, and ultimately damage your sender reputation, if you have such in your Newsletter list.

The Risk of Catch-all Policies

The bad news is that 40% of B2B email servers are catch-all servers. This means that even though your email messages may be delivered to begin with, you run a huge risk of eventually being labelled as spam, and ultimately having a damaged sender score.

Catch-all email servers can cause your business a lot of problems, including:
Increased Bounce Rate: some servers will automatically bounce messages and bounces with catch-all servers are very unpredictable.

Decreased Open Rate: Obviously, as you’re sending emails to addresses that don’t even exist, your open rate is going to decrease, therefore negatively impacting your return on marketing investment. This means you will spend more time chasing dead end leads.

Damaged Sender Reputation: As mentioned previously in this blog post, higher bounce rates, and invalid addresses on your database can damage your sender reputation. Catch-all policies can play a big part in your domain being punished or even blacklisted from sending email campaigns.

How to Detect Catch-all Servers

The most frustrating part of catch-all servers is that email verification services are unable to detect them. The only way to verify a catch-all domain exists, is to send an actual email to an address you know doesn’t exist within a domain. However, if you do this on your own, it can seriously damage your sender reputation.

At Marketing Monkeys, we often set up drip campaigns, with emails that have an opt-in, but show as a catch-all email so we can safely see any catch-all emails on our client’s database. We gradually mix those emails into campaigns and send-outs and try to manage the bounces below a critical threshold.

There is no 100% accurate way to verify these emails, but this method is the most accurate. Get in touch with our team today to see how they can help to detect catch-all emails.


Email verification is an often-overlooked aspect by email marketers, and some don’t even know the necessity of verifying the contacts in your database. With 9 out of 10 marketers using email marketing, it’s important that you maintain a healthy sender score to help maximize your revenue and avoid any further issues with emails unable to be delivered.
To see how our experts can help you validate your email database and clear out any addresses that could be damaging your sender score, get in touch today.

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