Email Marketing Sponsored Technology

What Is the Best Email Verification API?

Email marketing is not dead. In fact, it continues to work well for many companies. Experts even claim it to have a higher conversion rate in comparison to search engine and social media marketing combined.

However, email marketing success heavily depends on the overall validity of one’s email database. You see, no one – email marketers most of all – wants to be blacklisted as a spammer. Yet the chances of this happening are quite high. Accounts that receive numerous email bounces are heavily scrutinized in this regard.

But how can one know for certain if they are sending emails to active inboxes? Do you have time to go through hundreds or even thousands of them checking each one separately? The good news is that there are email verification services capable of solving such concerns.

In this post, I want to provide you with a list of the best email verification APIs to consider for your marketing efforts. But first thing first, how do you choose an email verifier application?

Table of contents

  • Criteria for the best email verification API
  • Product 1
  • Product 2
  • Product 3
  • Product 4
  • Product 5
  • Product 6
  • Product 7
  • Product 8
  • Product 9
  • Product 10
  • Summing up

Criteria for the Best Email Verification API

All of the email checking products that I have evaluated in this post can carry out the standard procedures of verifying formats, the existence of mailboxes, and the cleaning up of email lists to minimize penalties to sender score. For me, these three are the three main criteria based on which users can select the best email verification API for their needs:

Capabilities – This includes how good an email verification service is when it comes to performing checks. Some companies offer additional testing and validation protocols while others don’t. The delivery rates, integration, and the speed at which lists are processed are also things we keep in mind when assessing each provider’s features.

Documentation – I have looked at how these companies supply their customers with the proper guidance in getting started and if users can combine their existing apps with each product. The documentation can come by way of the regular API docs, a knowledge base, or a frequently asked questions (FAQs) page.

Payment plans – Not all of these services offer the same structure with regards to payment plans. Some of them charge a monthly or yearly fee while others will be based on a pay-as-you-go deal. There are also those that offer credits which are consumed depending on the package you paid for and are renewed daily. 

Now, before we proceed with the list of providers, it’s important to mention that the capacity to verify inboxes before contacting recipients offers several advantages. These include the ability to improve marketing campaign results, ensure that contact addresses are valid, and identify potentially harmful ones that could lead to abuse. 

Naturally, all products aren’t equal on these points with varying features. It falls on you to decide which would be the best match for your needs.

Product 1


Email Verification API aims to eliminate bounced emails in order to improve sender score and email campaign quality. It does this by utilizing an email verification system that prevents users from signing up with disposable emails. This ensures that only real personal or business email addresses can be registered when the software is active. It can also help organizations avoid being exploited by individuals who may be signing up to abuse free trial services, promos, and the like.

Various attributes are examined by the API including: 

  • Syntax – This checks whether an email address is compliant with the IETF (Internet Engineering Task Force) standards, acting as proof that it follows an open and well-documented process;
  • Typos and curse words – Scans the address input for common typographical errors, obscene language, and fake email patterns;
  • Disposable email addresses – Recognizes addresses coming from 10MinuteMail, Mailinator, GuerrillaMail, and other known disposable email address providers;
  • Mail server existence – DNS MX (Domain Name System Mail Exchanger) records are used to inspect the availability of an email address’ domain;
  • Mailbox existence – Email addresses are checked to see if they exist and can receive messages through SMTP (Simple Mail Transfer Protocol) connection and email-sending emulation methods;
  • Catch-all email address – Ensures that email addresses in the database are not generic or meant to be used for catching all nondesired messages.

The Email Verification API provides an online Bulk Email Validation service which allows users to upload existing data and then obtain the result in either CSV, JSON or XML formats. 

Once a document has been transferred, certain fields will start to fill up with various results. It’s possible to check the date and the time the file was uploaded and processed, the total number of emails detected in the input, how many of these contacts were processed successfully, and more. This capability practically speeds up the checking and validation process for email addresses and is able to go through thousands of contacts in a short time.


For documentation, the company has a page where customers can learn about the product and its features. In this section, one can study the required and optional input parameters, sample output available in both JSON and XML, and how certain attributes work. There are examples of the usage limit errors illustrating what happens when users reach the maximum number of allowed queries. Here customers can also obtain the link to check their current account balance information.

A guide on their bulk processing capability is also available in a separate documentation page. Found here are tips on how to perform requests, check the status of a request, get results for both processed and invalid emails along with the usage rules for the API.

Payment plans

Users that sign up for a trial of the API are provided with 1,000 email ID checks for free each month. From there, you can choose to expand on available queries through a one-time purchase, a monthly deal or a yearly subscription. There are  

documentation page. Found here are tips on how to perform requests, check the status of a request, get results for both processed and invalid emails along with the usage rules for the API.

Payment plans

Users that sign up for a trial of the API are provided with 1,000 email ID checks for free each month. From there, you can choose to expand on available queries through a one-time purchase, a monthly deal or a yearly subscription. There are

Product 2


Verifalia claims to make use of the RESTful API which works by retesting emails at certain intervals to avoid being suspected of spamming. This ability lets the software identify mailboxes that are made unavailable in the meantime due to a mail server’s protection protocols

Regarding processing, the company claims that single-address API requests can be processed in less than 1 second. The results can then be obtained in either an Excel spreadsheet or in .CSV file format. 

Among other attributes their verification checks include:

  • Address syntax
  • Domain
  • Disposable email
  • Mail exchange
  • Catch-all address
  • SMTP


A reference guide to their API is available for developers to understand how to use their product effectively. In this page, users can learn about the SDKs (Software Development Kit) they employ, how their authentication process works, what needs to be done prior to validating email lists and how to manage their account.

Verifalia also has a knowledge base that provides solutions to both non-technical and technical aspects of its services. Here it’s possible to find answers to general questions, sub-accounts, email validations, and pricing.

Payment plans

Customers can register for a free account which gives them continuous access to the client dashboard, a few levels of service and their API. This deal comes with free credits each day allowing at least 25 standard validation checks to be made. They also offer a variety of monthly plans which can be paid each month, quarterly or on a yearly basis. 

Product 3


ZeroBounce works by searching for possible spam traps including domains known for malicious behavior. Its API can be used to run checks on email addresses, matching them with profiles found on social media so it can fill in any missing fields from a list of contacts.

Their servers begin processing email lists once the data has been uploaded. It’s important to note that it can take approximately one to three hours for 100,000 addresses to be validated by the software. 


The company behind ZeroBounce has prepared a guide that is intended to assist customers when using their API. Tips on getting started, how email scoring works, integrations, account management, and more are found in their documentation page. An explanation of their data protection, privacy policy, and terms are all outlined here to ensure that everyone is aware of their rights and responsibilities. 

Payment plans

Signing up for their “Freemium” plan will grant access to detailed status codes, 24-hour customer support, 1,200 credits annually and more. Registering for this option is supposedly ‘free for life’ but there are limits to the email validation choices provided. From there users can decide whether they want to choose a pay-as-you-go plan, get a monthly subscription or opt for an enterprise scheme. 

Product 4


XVerify works just like most email validation tools wherein it ensures that all unique addresses are registered at their current domains. The company guarantees that they filter every email through their fraud protection system, ensuring that no temporary account or those linked with malicious domains are accepted.

Their API performs checks on the syntax and domains of addresses while it actively monitors for blacklisted emails. They also state that their program has an accuracy of 98% on all major email domains like Gmail, AOL, and Yahoo.


Documentation on the email verification API can be found as a separate page on the website. Here users can learn how to get started with the product, troubleshoot common errors, perform requests, upload files, implement JavaScript, and more. Furthermore, there is a small section that answers frequently asked questions to assist in resolving issues.

Payment plans

Unlike the previous companies, XVerify offers pay-as-you-go plans which will depend on customer requirements. There are various options to choose from with scaling prices. The higher the number of email verifications users sign up for, the lower their price per email becomes.

There are no minimum requirements when it comes to their API’s pricing, and there are no setup fees either. It’s also possible to choose between three currencies (USD, EUR, and GBP) when calculating for cost at the website.

Product 5


Email lists that are sent to BulkEmailChecker are said to be verified against a minimum of 17-factor tests while being filtered from a growing list of disposable email providers. When receiving results from the API, users can expect to have all duplicates removed plus all verified emails are claimed to be RFC (Requests for Comments) compliant. Their system filters role accounts and invalid DNS entries and can carry out an SMTP test to see a mailbox is active and can receive messages.

Customers using platforms like MailChimp and Mailget can also integrate them with their Bulk Email Checker account for extra precaution. 


As of now, Bulk Email Checker does not provide any form of documentation regarding their API.

Payment plans

The company offers packages that are bought with a one-time fee, are advertised as hassle-free, and with no strings attached. The email validations customers can get will depend on the usage and will scale upwards in price. Apart from the standard choices, there are also two enterprise options for those looking to verify a huge amount of addresses.

Product 6


Data validations API for email verification guarantees 99% deliverability when using their list cleaning service. Their bulk capability is said to be swift and comprehensive with documents returned to customers having Email Assurance grades that range from A+ to F. A free report on email lists can also be obtained when using the product.

Integrating the email list validation process using DataValidation and other apps like MailGun and MailChimp is also possible.


There is a complete guide on using the DataValidation API on the company’s website. Their documentation page provides an introduction to their software, examples on workflows, how their real-time validation operates, and many references on performing certain actions.

A knowledge base section can also be found. Here the company basically answers commonly asked questions regarding topics like how the product works, accounts and billing, getting started, and email assurance grades.

Payment plans

DataValidation offers price tiers for their service which will depend on the number of emails that are required by each customer. Preset packs can be found here providing a certain amount of verifications. These do not expire and can be used whenever needed. It is also possible to find monthly, quarterly, semi-annual, and annual subscriptions available at the website.

Product 7


Email lists that are sent to NeverBounce for verification are said to go through more than 20 steps in its proprietary cleaning process. Each email is supposedly checked at least 75 times before it is returned to the user. All email types are validated ranging from small to major providers such as Gmail and Yahoo.

The results that are obtained from the software are supplied into 5 categories: valid, invalid, accept all, unknown, and disposable. These files can be downloaded in either the common presets or customized based on user preferences.


A guide on their API is available at their website outlining aspects on how to get started, verify an email or a list, and run a free analysis. There are also tips on how to use their JavaScript widget and information on the various programming languages they support.

For users looking for answers, their help desk page can assist in resolving some of the most frequent concerns. Different topics can be found here such as on pricing and billing, downloading results, working with CSVs and list reviews. 

Payment plans

When talking about their payment options, NeverBounce provides scaling pay-as-you-go deals depending on the needs of their customers. Enterprise packages are available plus there is a free calculator on their Pricing page to learn how much you’d have to pay for a certain number of email verifications. 

Product 8


QuickEmailVerification provides a batch email validation service that can be carried out by uploading the CSV address lists to their servers. Their online system works by testing email addresses against several forms of verification beginning from the basic RFC syntax all the way to the deeper SMTP checking. Users can choose to integrate their REST API directly with their website or application to confirm addresses in real time.

The company behind the product states that it is 95% accurate and allows verifying 200,000 emails in less than three hours. Results are provided in a detailed report with all of the identified and cleaned emails within a separate mailing list.


Customers interested in learning how their bulk and real-time email verification features work can read all about it in their documentation page. Here, it’s possible to find out how to integrate the API with various apps and platforms such as Drip, Marketo, GetResponse, MailChimp, HubSpot and more. also has a section that’s dedicated to answering frequently asked questions from their clients. Most of the solutions provided here are about the general issues normally experienced by their users.

Payment plans

Currently, two mail email verification plans are offered by the company: one time and daily. Their payment scheme allows users to choose between getting persistent credits that do not expire or a balance that replenishes daily. The first one is their pay-as-you-go deal that doesn’t have a timeline and has custom plans available. Meanwhile the latter provides users with credits every 24 hours for more consistent needs. 

Product 9


The company behind claims to provide features that are best suited for enterprises. Their API can integrate with Google Sheets and Microsoft Excel which allows users to perform validations directly on their spreadsheets.

Furthermore, it supports such email providers as Hotmail, AOL, and Yahoo. Their software is capable of checking for spam traps, honey pots, disposables, offensive words, and more.


Unfortunately, the website does not have any sort of guide, knowledge base or FAQs page at this time.

Payment plans

Those who wish to try the product before making any commitments can sign up for a free account which comes with 100 email verifications for each user. They offer the standard pay-as-you-go pricing as well as unique deals for people looking for more.

Product 10


The email validation API from is said to have a 96% deliverability when it comes to its capacity. This product can perform checks for email syntaxes, MX records, MX server connections, free email providers, disposables, suppressed emails, duplicate addresses, and a few more.


The website provides separate pages on guides for developers, discussing aspects on their email APIs, SDK modules, integrations, and extensions. A knowledge base can be found here as well. It tackles common issues in terms of the general, marketing, and technical aspects of their product. Finally, a section that outlines frequently asked questions is also available.

Payment plans

Signing up for a free trial will grant users approximately 300 queries that are valid for 30 days. From there users can choose to subscribe to other monthly API plans that normally scale depending on the need. There are also options for bulk validations coming with varying response times depending on the scheme chosen. 

And there you have it – some of the finest email verification APIs available today. It’s important to note that the products listed in this article are only meant as a guide to let readers know what to expect from these providers. By following the criteria above, users should have a clearer understanding of what they want and what they should pay attention to when searching for the best email verification API.

About the author


Jonathan Zhang

Jonathan Zhang is the founder and CEO of Threat Intelligence Platform (TIP) — a data, tool, and API provider that specializes in automated threat detection, security analysis and threat intelligence solutions for Fortune 1000 and cyber-security companies. TIP is part of the Whois API Inc. family which is a trusted intelligence vendor by over 50,000 clients.