Top 5 free email validation APIs

Last Updated Apr 12, 2023
Emma Jagger

Engineer, maker, Google alumna, CMU grad

Table of Contents:

For any e-commerce business, maintaining up to date contact details for customers is critical. So here are the top five free APIs for email verification. Each one is a true free email verifier, limited only by the number of API calls (trial versions have no place here).

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What is an email validation API?

An email verification tool helps businesses validate email addresses and maintain a clean customer database free of invalid addresses. Some email APIs may offer additional features, but if you’re seeking a more detailed analysis than this round up, check out the best email validation and verification APIs.

The free email validation APIs we're going to look at today are:

  • Abstract Email Validation and Verification - 100 free calls per month
  • Zerobounce - 100 free calls per month
  • Mailboxlayer - 100 free calls per month
  • Reacher - 50 free calls per month
  • Hunter - 50 free calls per month
Sending email, image courtesy of Pixabay

What are the best free email validation APIs? 

Any organization that depends upon customers, visitors or subscribers needs to verify email to ensure that it’s maintaining an accurate email list. As complex as this might sound, it’s all about being able to get emails into a mailbox. Each service below can be counted amongst the best.

Abstract API

This free email verifier is built on a REST API and is easily implemented with code examples on the website.


This email checker is capable of returning a wide range of potentially useful information alongside detecting invalid email addresses. It can also detect disposable email providers, detect whether MX records (mail exchange records that specify the email server) can be found, provide a quality score that reflects Abstract’s confidence level in the address data provided, and more.

Free quota

100 API calls per month at one request per second.


  • Feature rich
  • Fast and stable
  • Database of free and disposable email providers updated regularly
  • Easy to implement
  • Email address suggestion to help avoid invalid email addresses


  • Marketing specific functionality may not be fully fledged
Email in online marketing, image courtesy of Pixabay


This email verification tool is targeted at email marketers who need to ensure that they minimize bounce rate to make sure their business maximize ROI.


As well as checking that an address is valid, this email verification tool can also do IP address geolocation, is GDPR and SOC 2 compliant and allows the testing of email addresses on the Zerobounce mail server before emails are sent. 

Free quota

100 per month.


  • Detect whether addresses accept mail
  • Automatically scores each email in an email list
  • Validate whether a sender’s email domain is blacklisted to maximize email deliverability
  • Validate email addresses to minimize hard bounces
  • Can be integrated with other tools


  • No integrated analytics for this tool which is targeted at email marketing


This is promoted as a simple REST API for assessing the deliverability of emails.


Like other APIs, this can detect whether an email address exists, but also offers other features. It can detect MX records, disposable emails, a query capability for a single email, and more.

Free quota

100 per month.


  • Offers extended usage statistics
  • Email address provider database updated daily
  • Provides a deliverability score


  • Not feature rich


Unlike other options, this email authentication tool is open source. Be aware that ‘open source’ means that the software may be developed on an ad-hoc basis. 


This email verifier uses real time checks to connect to mail servers so that bad data is minimized. It can detect whether an address is a ‘catchall address’ to which all invalid emails are routed. 

Free quota

50 per month and also free forever for personal use.


  • Free for personal use
  • Open source enables greater transparency
  • Integrations are easy


  • Open source can mean irregular updates and the last update for Reacher was May 2020
  • Not feature rich and this is unlikely to change if development isn’t picked up


This service is targeted to enabling email marketers in a business to detect invalid emails. In this use case, being able to verify an email address is critical.


An email marketer could use this service to push potential leads to a CRM making it easier to manage contact lists. It also offers confidence scores for addresses so that users can make a call on whether emails to that address are really going to land in an inbox or a spam folder. It’s also capable of checking webmail email addresses like Gmail. 

Free quota

50 per month. 


  • Assesses the deliverability of emails
  • Uses a unique data set


  • Unclear how often the unique data set is updated

Why is email validation important?

The capability to verify an email address is important for a range of reasons. Let’s have a look at three of the big ones.

Email validation can improve bounce rates

If a business isn’t using an email checker, then it’s unlikely to have any way of understanding whether any email addresses are current. Then, the bounce rate for email campaigns will inevitably increase over time. It can also help ensure that your database, which you need to keep clean, isn’t fed a disposable email address.

Bear in mind as well that, if an organization (not just businesses) is operating in the EU, then it’s required to comply with GDPR (General Data Protection Regulation). This includes the requirement for reasonable efforts to be made that data on individuals is kept up to date. Violations of GDPR can lead to fines of up to 20 million euros or 4% of global turnover from the previous year. 

Avoid being marked as spam

A big reason to maintain accurate email addresses is that email servers will maintain their own defenses against spam. So, over time, a server that repeatedly sends messages to invalid mail addresses may lead to that entire domain being blacklisted. So, your business might think that it’s sending to subscribers inboxes, but all the emails are actually getting rerouted to spam traps.

Worse, that can all lead to a business domain attracting a poor sender reputation, so if that anti-spam software is widely used, a business may see extremely poor returns on its email marketing.

No spam, image courtesy of Pixabay

Improve user sign-up data accuracy

These tools can check the format of an email address to ensure that, when a user signs up, their email address meets recognized formats. After all, ‘fat finger’ errors where a user accidentally hits the wrong key are something we all experience. Also, auto-correct can be a source of errors. Proactively minimizing such bad data will help keep your email address clean which, in turn, will help prevent the server of a business developing a low sender reputation.

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Validate & verify emails instantly using Abstract's API.
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