Business Sponsored Technology

Top 3 Email Verification APIs

Though full of potential, email marketing is surely no walk in the park. Every organization is different. Competition is tough. Attention span is going down. No hard rules are in place. That said, success still requires following some best practices.

For instance, it’s crucial that the email addresses accumulated in lists and databases are valid ones. Otherwise, how can marketers expect that their messages get well-received on the other end? After all, your recipients won’t be able to read your emails if they aren’t getting them in the first place.

Years ago, marketing professionals couldn’t check whether an inbox was still active or not. They had to learn by experience — often being flagged as spammers and penalizing their sender scores. Fortunately, there are technologies today that offer email verification services to tackle these problems.

This article evaluates a few of the best email verification API products available right now. But before we begin, let’s take a look at the criteria to guide us through the decision process.

Criteria in Choosing the Best Email Verification API

The three categories below are intended to assist users in selecting the appropriate API that is suitable for their needs. These are the:

  • Attributes – How proficient is an email verification service when carrying out validations? What’s the number of email addresses that can be reviewed at once? How fast can results get delivered? How well does an email verification API integrates with other apps?
  • User guides – The second point to consider is how well these API verification companies provide guidance to end users. Tips on getting started and how certain features can be incorporated with others is to be examined. Supporting documents can take the form of API manuals, knowledge bases, FAQs pages, or all of the above.
  • Cost – Payment plans for the products on the market are not the same. Some companies let people sign up for a monthly or yearly fee while others offer services exclusively through a pay-as-you-go scheme. There are also providers that have packages with varying credits that are replenished daily. The APIs presented below have a minimum of two choices at the very least.

Now that we know what criteria to pay attention to, let’s proceed with the review of the best email verification APIs currently available on the market.


The Email Verification API is owned by Whois API, Inc. – a big data company in Los Angeles, California that specializes in domain, Whois, DNS, IP, and threat intelligence information for various industries. More information is available on


This software aims to improve users’ sending score while enhancing the quality of their email campaigns. A distinct aspect of the product is that it employs an email verification system that disallows visitors to sign up with disposable email addresses. This protocol ensures that all contact details received are real which, among other benefits, reduces the risk of freemium features and plans being abused.

When validating emails, this API takes into account the following attributes:

  • Syntax
  • Typos and curse words
  • Disposable email addresses
  • Mail server existence
  • Mailbox existence
  • Catch-all email address

Whois API also provides access to their Bulk Email Verification service. This mass email verifier feature lets users upload their email databases which will be processed and cleaned accordingly. The latter is important in guaranteeing that all contacts in a list are confirmed to be legitimate, operational, and free from fraud. It’s possible to obtain results in either XML, CSV or JSON formats.

User guides

The standard API documents are provided on the company’s website. Outlined here are tips on carrying out requests, how to input various parameters, and detailed explanation of each attribute. If you’re interested to know how results look like, a sample output can be obtained in either JSON or XML.

A rundown of the bulk verification capabilities is available on a separate documentation page. This section also includes a list of all possible errors that users can encounter while operating the product.

Lastly, in the site’s integrations page, users can find the links to their GitHub, packages, and guides to some of the developer libraries currently being supported. 

Payment options

Signing up for a free subscription plan will provide registrants with 1,000 queries each month. If users need more, they can choose to get either a one-time purchase or monthly or yearly subscription. The first option lets customers pay only for the number of credits they wish to use, guaranteeing that these credits do not expire. The second and third choices are pretty straightforward as users pay a fixed amount every month or year for a certain number of lookups.


Verifalia is an email validation service that was created by Cobisi – a software development tools provider.


Verifalia’s API offers validation and integration of contact databases into existing systems for incoming email addresses. Their process goes through several stages yet only takes a few seconds to accomplish. The company also claims that the product is capable of checking for syntax, domain, mail exchanger, mailbox confirmation, catch-all, temporary unavailability, and more. 

User guides

Documentation on this API provides guidance on how its authentication features work, which endpoints are being used, as well as a description of their status codes and tips to get email validations started. A knowledge base answering the commonly asked questions from their clients is also available. 

Payment options

Verifalia offers a free account for users who want to test how the product works before signing up for a paid option. The trial plan includes ongoing access to their API and comes with enough free credits to perform 25 standard email validations daily. It’s possible to increase this balance by purchasing additional credit packs or avail of their monthly packages.


ZeroBounce API is owned by an American company with headquarters in the US.


The company’s product operates by checking all email addresses within a contact list and then matches these with their appropriate social media profiles. According to ZeroBounce, their email verification system comprises the following:

  • Email bounce validator – which eliminates faulty email addresses;
  • Spam trap & abuse email verifier – which identifies risky email addresses and cleans existing lists;
  • AI email scoring – which employs artificial intelligence to rank email address values.

Once validation is finished, users can choose the results that they want to show up and then download the report.

User guides

Their API’s documentation page explains in detail how their AI email scoring, email list verification, and integration features work. Here it’s possible to find guidance on integrating the product with such platforms as AWeber, CloudFlare, Constant Contact, Hubspot, and MailChimp. This same section also provides the answers to their frequently asked questions.

Payment options

As for their plans, one can expect their “Freemium” subscription to have free credits on a monthly basis together with access to detailed status codes, IP address geolocation, validation tools, and 24-hour support. Clients with more particular goals can select either their pay-as-you-go, monthly, or price-per-email payment schemes. 

The products reviewed in this article are probably the top three available right now — for a more extensive comparison, feel free to check this other article on the best email verification API. Important note: While the criteria listed above may serve as a starting point for readers to find the product that can meet their objectives, the final decision will still depend on specific user needs.

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.