How email verification can optimize your transactional email sending

Amy Elliott
· 6 min read · Tips and resources · August 24th, 2022
Your recipients’ email addresses are your most valuable asset—but how can you be sure that they’re all accurate? Email verification is the best way to keep your email list free from invalid email addresses, ensuring optimum deliverability and inbox placement.

If you’re sending transactional emails, you might be wondering why you’d need to validate your recipients’ email addresses. After all, they signed up to your service, right? Surely they used an accurate and valid email address! 

Maybe not. Plenty of users submit invalid emails by way of typo, disposable accounts or even completely fake email addresses. And then there are the few that leave their job or let an email address go inactive and then forget to update this information. While these users may be missing your important transactional messages, it can also spell trouble for your email deliverability. 

In this article, we’ll explain the what, who and why of email verification and give you tips on how to maintain good email list hygiene. By the end, you’ll be able to start verifying your recipients’ emails right from MailerSend!

Who needs email verification?

Anyone sending emails to customers, users or subscribers needs email verification. An unverified email list can potentially harm the sending reputation and deliverability of anyone sending emails.

The longer you leave your recipients’ emails unchecked, the more likely it is that some of them will become inactive—you might even end up with a few spam traps. The larger the number of bad email addresses, the less likely Internet Service Providers (ISPs) are to deliver your emails. Your sender reputation is negatively affected. 

This means that your customers or users might not receive important emails. Whether you provide a service, run an online shop or e-commerce business, or are a SaaS provider, maintaining strong customer relationships is crucial. Your transactional messaging is a key element of this relationship-building. It provides a direct line of communication, so it’s important to practice good email list hygiene to maintain it.

How you can benefit from email verification

With transactional email you don’t need to worry about the General Data Protection Regulation (GDPR), CAN-SPAM or other anti-spam laws. However, the benefits of validating your recipients’ emails are far-reaching, and can even affect your bottom line. 

  • Correct customer information: In the ‘80s, an up-to-date and accurate rolodex was every businessperson’s best friend. Now we’ve gone digital, having the correct customer information is just as important, but the potential for inaccuracy has grown. Email verification helps to combat this, keeping your email list fresh and clean. 

  • Increased conversions: The more users or customers that enter a valid email address, the more opportunities you’ll have to convert them, from completing next steps in the account setup process to sending abandoned cart emails. 

  • Better engagement: A more accurate recipient list will lead to increased click and open rates in your transactional emails. 

  • Lower bounce rates: Email checkers help to identify email addresses that are likely to hard bounce. You’ll get more emails delivered and improve your deliverability. 

  • Good sender reputation and deliverability: Low engagement rates and signs of spammy activity (for example, sending to inactive/spam trap emails or continuing to try sending to the same invalid email addresses) can have a negative impact on your sender reputation thus decreasing your deliverability.  

  • Reduced sending costs: By only sending emails to real, valid recipients, you could potentially lower how much you spend each month on sending transactional emails. 

  • More accurate results: If you eliminate fake or invalid email addresses, your analytics will reflect more accurate results, enabling you to make better informed decisions about your sending strategy.

Bulk email verification

Email validation tools, including MailerSend’s inbuilt feature, allow users to verify whole email lists in bulk. 

Bulk email verification allows you to quickly and effortlessly clean up an existing list. With this method, all you need to do is upload your entire email list as a CSV and MailerSend will get to work validating each and every email address. You’ll get your results in minutes, which you’ll then be able to download and use to clean your list.

Getting started with email verification

With MailerSend’s inbuilt email verification service, you can easily verify your email list in minutes directly from within the app. Let’s take a look at how you can upload your email list.

Verify an existing email list

1. In the app, navigate to Email verification from the left-hand menu. 

A view of the MailerSend dashboard with Email verification highlighted in the navigation menu.

2. Click the Verify new list button and upload your CSV file of email addresses. 

A view of the Email verification page in MailerSend with the Verify new list button highlighted.
Note: If the file has more than one column containing emails, you will be asked to confirm which column of emails you want to verify.

 3. When the file is imported, you will be informed of how many credits you need to verify the list. If you already have enough credits, you can go ahead and click Verify list. If you need to purchase additional credits, you can do so on the Plan & billing page in the Add-ons section, by clicking on Order

A view of the pop-up when the CSV file upload is complete.
Note: One credit is equal to one email address verification.

After selecting Verify list, the verification process will happen in the background, so you’re free to visit other areas of the app while you wait. Once finished, you can head back to the Email verification page to view and download your results. 

Have a look at our Knowledge base article to learn more about verifying an existing email list and check out the email verification API reference.

Understanding email verification results in MailerSend

MailerSend’s email verification tool splits your results into three categories—valid, risky and do not send—to make it easy to analyze and sort your recipients’ email addresses based on whether you want to add them to your suppressions list.

A view of the email verification results in MailerSend.

Let’s take a look at the different results and what they mean. 

Valid 🥳

Email addresses with this status are safe to send to—awesome!

Risky ⚠️

You should only send to these email addresses with caution as they may be undeliverable or be attached to an inbox that isn’t checked frequently or at all. 

  • Catch_all: The recipient’s mail server can accept incoming messages, however it’s not guaranteed that it belongs to a real person

  • Mailbox_full: The recipient’s inbox is full and may not be able to accept new incoming emails

  • Role_based: The email address is role-based (for example,, and therefore may not belong to an individual but a group of people. 

  • Unknown: We are unable to determine if the email is valid

Do not send 🙅

These are the email addresses that you should add to your suppressions list (blocklist) and cease sending to.

  • Syntax_error: The email address is not valid

  • Typo: The email address has a typo. You may be able to correct the email address and retest if the typo is obvious, for example, (gmail)

  • Mailbox_not_found: The inbox does not exist

  • Disposable: A disposable email address is a temporary email address that people use to avoid getting spam or promotional emails delivered to their inbox

  • Mailbox_blocked: The recipient’s mailbox is blocked by its service provider due to poor sending practices

Clean up your email list now!

Verifying your recipients’ email addresses is the best way to keep your transactional sendings performing at their best. You’ll be able to maintain a clean, healthy email list, keep customer and user information up to date, improve your sender reputation and deliverability, and continue to build strong relationships with recipients. You might even save a buck or two as well!

Try out MailerSend’s email verification tool from within the app, let us know what you think and tell us about your experience with email list cleaning in the comments.

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Amy Elliott
I’m Amy, Content Writer at MailerSend. As a child, I dreamt about writing a book and practiced by tearing pages from an A4 notepad and binding them with sugar paper. The book is pending but in the meantime, I love taking a deep dive into technical topics and sharing insights on email metrics and deliverability.