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What to look for in an email verification tool

Email validation tools help to ensure a successful marketing campaign. Discover what factors to consider to guarantee effective and efficient email validation and what you should look for in an email validation tool.



Marketers know how important growing a list of contacts is to the success of a business. The more people who give you permission to deliver messages to their inboxes, the more chances there are to increase revenue.

That’s probably why Mailjet’s report, “Email in an evolving economy”, found that more than 45% of marketers surveyed chose List building as one of the top practices of a successful email program.

List growth is a sign that your brand is doing a lot of things right. But it can be maddening when what you think is a new subscriber turns out to be an invalid email address.

Maybe someone made a typo when filling out your form. Maybe they used a disposable email address. Whatever the case, you thought you acquired a new lead, but that contact is nothing but dead weight. It’s also frustrating to watch your bounce rate climb as outdated contact information erodes the quality of your email list.

In situations like these, an email verification tool is extremely valuable.

What is an email verification tool?

Email verification (also known as email validation) is the process of authenticating an email address to see if it’s legitimate.  Of course, a valid email address is correctly formatted, connected to a real email account, and has an actual person behind it.

While you could try to validate your own contacts, manual email verification would be time-consuming and unreliable. That’s why most senders use an automated email validation service, like Email validations from Mailgun Optimize.

An email verification tool makes it easy to separate quality subscribers from bad email addresses and fake contact information. It can also catch issues with email addresses before they end up on your list.

Why should you use an email verification tool?

You might be wondering why this is such a big deal. Can a bad email address cause any actual harm? Can an email verification tool make any noticeable difference in the performance and success of your marketing strategy?

The answer to both those questions is YES. Here are three reasons why you should use an email verification tool:

1. Get accurate email metrics

Invalid email addresses will drag down your stats. That’s because those non-existent contacts won’t open and engage with anything. So, you won’t get a clear picture of campaign performance. Your open rates and click rates will be lower, and your bounce rate will be higher.

2. Make list cleaning easier

Just like a good spring cleaning, email lists need to be scrubbed at least once a year. People abandon email accounts. They move to different jobs or graduate and change contact information. Sometimes, old, unused email addresses turn into recycled spam traps, which need to be removed to avoid deliverability issues.

If your subscriber list is large, manually identifying outdated or inactive contacts that should be removed could be a huge pain in the neck. But an email verification tool helps automate the job, making things fast and straightforward.

3. Improve deliverability and maintain your reputation

If your email list gets cluttered with fake emails and outdated contact information, it will start to look spammy. That’s because spammers often use lists full of old emails as well as spam traps. The same goes for purchased lists.

When your list is a mess, mailbox providers will take notice, and your email sender reputation will decline. That means your emails may be more likely to land in the junk folder than the inbox.

On the other hand, a clean email list full of verified contacts who've given consent to be contacted is a sign that you’re a responsible sender that mailbox providers can trust. That trust greatly improves your chances of a higher inbox placement rate.

7 Key features of an email verification tool

If email validation is a service you need, there are some important considerations when choosing the right tool. Here are the most beneficial features for email address verification.

1. Bulk email verification

If you plan to use an email verification tool to conduct list cleaning, you’ll want to make sure it includes bulk verifications. That simply means you can upload a CSV or spreadsheet of your contacts and get a report back on the health and validity of the email addresses.

You will find plenty of “free” email verification tools online. However, these usually only allow you to check one email address at a time. We’re willing to be you won’t want to do that with your entire list.

Mailgun Optimize provides an option to try our email verification tool using a statistically significant portion of your list. This sort of test can clue you in if your email list is in poor health.

(By the way, if you want to quickly verify a single email address with Mailgun Optimize, you can do that too.)

Bulk email verification mockup

2. Real-time email validation

The best email verification tools can validate addresses at the point of signup. If someone fills out a form and makes a mistake, or tries to use a disposable/fake email, they’ll be notified that the address they entered isn’t valid.

That means you avoid needlessly losing new leads and subscribers. It also means people who really want to hear from you won’t be left wondering why you never sent them anything. Plus, real-time email validation helps you maintain good list hygiene. So, the next time you clean up your contacts, there will be less to remove from your list.

Mailgun Optimize’s real-time verification API complements the bulk email verifier, allowing you to verify a massive list and also validate emails as people submit their information.

3. Mailbox provider/MX record verification

An email address may look like it’s legitimate, but how do you know is an actual, active account? A good email validation tool will verify the existence of an address with the mailbox provider (MX record verification).

Mailgun Optimize’s email verification tool uses cached send data to verify addresses. Many other services use the broken SMTP handshake method to validate emails. But cached send data is faster and much more reliable.

4. Speed of verification

Whether it’s an email marketer doing some list cleaning, or a potential subscriber filling out a form, no one wants to sit around, twiddling their thumbs as they wait for verification to work. That’s why a fast email verification tool is a big benefit.

If you’re an online retailer that is validating emails at checkout, speedy verification could even mean the difference between someone completing an order or abandoning their cart.

Mailgun Optimize is known for its lightning-fast email verifications. We’re so confident in the speed of our tool, we even offer a service level agreement (SLA) based on the application’s performance. That’s a guarantee you won’t find anywhere else.

5. Identify role-based email and catch-all addresses

Role-based email addresses usually belong to a specific department or a distribution list within an organization. It could be something like

Role-based email addresses may be real, but they present some problems.  It may represent an account to which multiple people have access, or it could deliver your messages to a group of people. And neither of those situations is ideal.

Role-based emails also have compliance risks. If someone subscribes using an email account that several people use, you increase your risk of spam complaints. And that could end up getting you blocklisted. Even though someone may have used that email address to subscribe, everyone else may assume your messages are unsolicited, which makes you look like a spammer.

Catch-all email addresses serve a similar purpose. They could include or Sometimes, invalid email addresses end up getting delivered to catch-all mail servers. So, if someone wants to send a message to but the correct address is, the message still gets through. But it lands in the inbox – not Gerry’s inbox.

Most senders don’t want catch-all or role-based email addresses on their list because they are impersonal and can mess with your metrics, causing higher bounce rates and lower engagement. And that will eventually have a negative impact on email sender reputation.

6. Catch and fix typos

We all make the occasional typo. It’s part of what makes us human. But it’s surprisingly easy to mess up an email address.

Some of the most common email address typos happen in the domain name after the @ symbol in the address. For example, a contact accidentally misspells Gmail, Yahoo, or Hotmail. Without real-time verification that simple mistake could be a lost lead.

A tool like Mailgun Optimize catches those problems and even suggests the right fix before new contacts submit their information and an invalid email address ends up on your list.

Email verification API mockup

Email addresses also have unique grammar and syntax. In other words, they must follow a specific format: The verification process can also catch mistakes in email address formatting.

Furthermore, certain mailbox providers allow or disallow different characters and symbols. Mailgun Optimize’s verification process knows all about that. The service checks email addresses using RFC grammar rules so those “technical gotchas” won’t be a problem.

7. Email deliverability expertise

Finally, you’ll want to find a partner with a deep knowledge of how email works and a reliable infrastructure on which their email verification service is built.

Mailgun Optimize is built on infrastructure from Sinch Mailgun. Since 2010, Mailgun has been changing the way businesses send email with innovative technology and solid email infrastructure. Today, Mailgun sends more than 300 billion emails every year for businesses around the world.

To put it plainly, Mailgun understands how email works and what it takes to get messages delivered to the inbox. That knowledge and expertise extends to Mailgun Optimize.

Get a complete email deliverability suite

While email verifications are extremely helpful and important, Mailgun Optimize offers much more than that. It’s built to be a comprehensive email deliverability solution. That includes:

  • Inbox Placement: Get reports that predict where your emails will land, including breakdowns for specific mailbox providers.

  • Blocklist and spam trap monitoring: Catch deliverability issues before they become serious problems that impact business results.

  • Expert advice: While all our users receive customer support, select plans are eligible for a dedicated Technical Account Manager (TAM) and a custom strategy through our

    Deliverability Services.

Talk to a strategist today and find out what you can accomplish with the world’s best email deliverability platform. Or check out Mailgun Optimize pricing for details.

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