The 7 Best Email Verification APIs for Developers
A detailed analysis of the top email verification APIs for developers.
Verifying email addresses can help prevent high bounce rates and avoid damaging your sender reputation.
Fake email addresses can enter your audience list when:
- Bad actors sign up with fake addresses
- Users mistype their own addresses
- Users delete old inboxes
While you should supplement verification with other methods, like double opt-in and CAPTCHA, verifying email addresses can help prevent hard bounces from sending to invalid emails.
In this post, we'll explore the top APIs developers can use to verify email addresses and protect their deliverability.
Why you should trust us
Resend is an email platform built for developers.
We have tools like Deliverability Insights to help you improve your sender reputation. And we also offer personalized help from our team of email experts.
Email verification APIs typically work via three main steps: validation, MX record verification, and SMTP server verification.
- Syntax validation: This step checks for typos and non-compliance with the RFC 5322 standard. Invalid email addresses may include improperly formatted input, such as addresses that are missing a domain name or an @ symbol, or content that contains invalid characters or whitespace.
- MX record verification: MX records are a type of DNS record that helps to route emails. MX records need to exist and be set up properly; otherwise, emails sent to them will bounce.
- SMTP server verification: These services often ping SMTP servers to ensure that the servers exist and are ready to accept emails. This step can be complex and risky. Email verification APIs use a variety of safeguards in order to check SMTP servers without getting blocked or delivering inaccurate results.
Email verification APIs also take care of other considerations, such as creating blocklists for temporary email address services. So while it's technically possible to roll your own email verification, we strongly advise using an existing service to meet your needs and cover edge cases and complexities.
The best email verification APIs
Here are the top APIs we have evaluated:
1. Emailable
The most accurate email verification platform
Based on the criteria we evaluated, Emailable is Resend's top choice. It's reliable and accurate, and provides robust data enrichment.
Developers will enjoy a generous free tier, high processing speeds, and an emphasis on customer support.
Emailable features
- Data enrichment, including quality scores, mailbox full detection, no-reply detection, and suggested alternate spellings for mistyped domains
- Unlimited API keys, and the option to set them to public or private and live or test
- Supports local currencies in USD, AUD, BRL, CAD, EUR, GBP, MXN, and PHP
- Integration with 50+ apps, and SDKs for Node.js, Ruby, and Python
- Typical processing time is 30,000 verifications per minute, much faster than others
- Don't cache results for more than 5 minutes (so truly real time)
- SOC 2 type II and GDPR certified
- 99% deliverability guarantee
- 99.99% platform uptime
- 24/7 customer support
- 200,000+ customers
Pros
- Generous free tier
- High reliability and deliverability
- Reported processing speed is much faster than the other APIs we analyzed
Cons
- Some other solutions offer SDKs in more languages
Pricing
Emailable offers the most generous free tier out of all the solutions we've analyzed. They also offer reasonable paid verification rates.
- Free trial: every user gets 250 free verifications (1,000 with Resend partnership)
- Price per verification: $0.0021 - $0.0076
- Minimum purchase: $38 for 5,000 credits
- Credit expiration: never
- Subscriptions available: yes
They also have custom rate limits and batch sizes for Enterprise businesses.
View the Emailable pricing page for more details.
Emailable
Claim free Emailable credits as a Resend user.
https://emailable.com/partners/resend
Best use case
Based on the criteria we evaluated, Emailable is the best all-around email verification API. Emailable is highly accurate, provides detailed data enrichment, and works much faster than the other solutions.
In particular, hobbyists and indie developers will enjoy its generous free tier of 1,000 verifications for Resend customers.
2. ZeroBounce
Used by Netflix, Amazon, Airbnb, Disney, and more
ZeroBounce positions itself as "the #1 email verification API for 400,000+ clients." Used by large, big-name brands like Intel, Samsung, and Coca-Cola, it offers a 99% accuracy guarantee, custom allowlists and blocklists, and more.
ZeroBounce features
- 99% accuracy guarantee
- Data enrichment, including inferred first and last name, gender, and location
- Custom allowlists and blocklists
- Integrations with 50+ platforms, such as Salesforce, Shopify, and HubSpot
- SKDs for .NET, PHP, Python, Java, Swift, and more
- Typical processing time is 1-3 seconds per email
- SOC 2 type II and ISO 27001 certified
- HIPAA, GDPR, and CCPA compliant
Pros
- HIPAA compliant
- Custom allowlists and blocklists
- Data enrichment includes an inferred city, region, and country
Cons
- No detection for temporary email addresses
- The docs are complex and can be difficult to follow
Pricing
- Free trial: every user gets 100 free verifications
- Price per verification: $0.00225 - $0.009
- Minimum purchase: $20 for 2,000 verifications
- Credit expiration: never
- Subscriptions available: yes
View the ZeroBounce pricing page for more details.
Best use case
ZeroBounce is best for organizations that need compliance with HIPAA and other data privacy standards.
Inferred location provided by data enrichment can also aid companies with specific location-based needs.
3. NeverBounce
Deliver up to 99.9% of your emails with confidence.
NeverBounce is a popular email verification API. Highly accurate and with a solid customer base, it offers integrations with many popular tools.
NeverBounce features
- Deliverability rate of up to 99.9%
- Automated list cleaning tool
- 85+ integrations with tools like HubSpot, Marketo, and Mailchimp
- Typical processing time is 10,000 verifications in 2-10 minutes
- SDKs for Node.js, PHP, Python, Ruby, Go, Java, .NET
- 125,000+ users
- Used by companies like Dropbox, Asana, and Doordash
Pros
- Automated list cleaning tool
- Various integrations with other tools
- Large assortment of SDKs
Cons
- Only 10 free verifications per customer
- Credits expire a year after the purchase date
Pricing
- Free trial: 10 free verifications
- Price per verification: $0.002 - $0.008
- Minimum purchase: $8 for 1,000 verifications
- Credit expiration: one year from the date of purchase
- Subscriptions available: yes
View the NeverBounce pricing page for more details.
Best use case
NeverBounce is a good choice for organizations with medium-to-large email lists. It offers competitive pricing for 100,000 verifications, as well as an automatic list-cleaning tool for ongoing audience hygiene.
4. Kickbox
The most accurate email verification API
Kickbox is a popular email verification API, serving companies like Vrbo, Expedia, SeatGeek, and more.
While its stated accuracy rate is lower than the other APIs we evaluated, it makes up for the difference by refunding verifications that come back as unknown. Kickbox also provides a Slack channel for community and customer support, as well as a visual usage dashboard, making it a solid choice.
Kickbox features
- 95% accuracy guaranteed
- Unknown verification results are free
- Used by companies like Sonos, Reddit, Notion, Zapier, and others
- Data enrichment includes a reason, suggested alternate spellings, free and disposable email detection, and more
- Batch verification job API for up to 1 million email addresses per batch
- The API dashboard includes response rate data visualizations
- Supported documentation languages include Node.js, Ruby, Python, and PHP
- Typical processing time is 100,000 verifications in about an hour
- GDPR and CCPA compliant
- SOC 2 certification coming soon
- 150,000+ users
- Dedicated Slack channel for customer support and community
Pros
- You won't be charged for that verification if a result comes back as unknown. You can verify that result later or use your credit to verify another email address.
- Data enrichment adds various additional insights to verifications.
- The API dashboard adds visualizations that other APIs don't offer.
Cons
- Only 100 free verifications per customer
- Verification credits expire one year from the date of purchase
- Lower accuracy rate than the other APIs that we evaluated
Pricing
- Free trial: 100 verifications
- Price per verification: $0.01 -$0.004
- Minimum purchase: $5 for 500
- Credit expiration: one year from the date of purchase
- Subscriptions available: no
- Unknown results are free
View the Kickbox pricing page for more details.
Best use case
Kickbox is a solid all-around choice, and a great choice for users looking to verify large email lists in one batch.
5. BriteVerify
The most accurate email verification API
BriteVerify is an email verification API by Validity. It sets itself apart by offering verification for phone numbers and addresses from the U.S. and Canada as well as emails.
BriteVerify features
- Documentation contains code examples for various languages, such as JavaScript, Go, C#, PHP, Ruby, and Swift
- Typical processing time is 4,000 email addresses per minute
- TrustRadius score of 8/10; 4/5 stars on G2
- Used by clients like Shutterstock and Farmers Insurance
- Dashboard visualizations for an easy-to-follow overview
- Download lists based on result; for example, only download the valid email addresses
- Integrations with Zapier, Salesforce, and other tools
Pros
- The API can also verify phone numbers and addresses from the U.S. and Canada
- The dashboard can help you view your results at a glance
Cons
- No free credits, so you can't try before you buy
- No dedicated SDKs
- Returns less information than other solutions that offer data enrichment
Pricing
- Free trial: none
- Price per verification: $0.0045 - $0.0080
- Minimum purchase: $40 for 5,000 credits
- Credit expiration: never
- Subscriptions available: upon request
View the BriteVerify pricing page for more details.
Best use case
BriteVerify is best for users who need to verify phone numbers and addresses from the U.S. and Canada, as well as emails.
6. Bouncer
Email Verification and Validation API designed for developers by developers
Bouncer touts a 100% total uptime and less than 2% unknown results.
With good ratings and a strong emphasis on security and customer support, Bouncer is a solid choice for email verification.
Bouncer features
- Security features, including MFA and the option to allow API calls only from specific IP addresses or ranges
- Customer support via video, chat, and email
- Organizations feature, which allows you to share credits and history of verifications, API keys, and more
- Data enrichment includes a score, a toxicity flag, and detection for full mailboxes and disposable email addresses
- Typical processing time is 180,000 email addresses per hour
- GDPR compliant
- Language examples in the docs include Python, JavaScript, PHP, Go, and Java
- Winners of various Capterra, EVS, and G2 awards
- Customers include T-Mobile, Airbnb, Toyota, Oracle, and others
Pros
- Customer support provides the option to video chat to get help
- Strong emphasis on security
- Tools for organizations that allow for sharing credits and API history
Cons
- No dedicated SDKs
Pricing
- Free trial: 100 free credits
- $8 for 1,000 verifications
- $35 for 5,000 verifications
- $400 for 100,000 verifications
- $2,000 for 1 million verifications
- Price per verification: $0.0020 - $0.0080
- Minimum purchase: $8 for 1,000 credits
- Credit expiration: never
- Subscriptions available: yes
View the Bouncer pricing page for more details.
Best use case
With a strong emphasis on security and specialized tools for organizations, including the option to only allow users and API calls from specific IP addresses or ranges, Bouncer is a great choice for teams.
Bouncer offers the lowest price out of all of the evaluated options for 1 million verifications, which makes it an economical choice for organizations with large email lists.
7. Mails.so
Simple, fast, and secure email validation service
Mails.so touts its simplicity, and integrations with no-code tools to set it apart.
Mails.so features
- 99.99% uptime
- Data enrichment includes a score, free email detection, and whether the MX records and domain are valid
- GDPR compliant
- Integrations with no-code solutions Zapier and Make
- Code examples in cURL, Python, JavaScript, Go, PHP, Ruby, Java
Pros
- 50% discount for nonprofits
- Zapier and Make integrations
Cons
- No dedicated SDKs
- Subscription-based, without the option to buy one-off credits. This means that credits expire when the month is over.
- Less robust documentation than other solutions
Pricing
This API has a different pricing structure from the others—a tiered, user-based subscription:
- Free: New users get 50 free credits.
- Pro: $48 per user per month, with 10,000 validations per month included.
- Business: $98 per user per month, with 50,000 validations per month.
- Unlimited: $498 per user per month, with an unlimited number of validations.
- Enterprise: $1,899 per user per month, also with unlimited validations. This level also includes a 99.99% guaranteed uptime SLA and priority support.
- Once users have reached their validation threshold, they can pay a per-validation fee for additional credits.
- 50% discount for nonprofits
View the Mails.so pricing page for more details.
Best use case
Mails.so is best for non-profits, as it offers a 50% discount. This is especially true for organizations that only need a handful of user seats, especially if they have a high volume of verifications and choose an unlimited plan.
What makes a great email verification API?
There are many email verification APIs with different benefits and pricing structures. Here is the list of features we evaluated:
- Capabilities: does the API allow for both bulk and real-time email verification?
- Reliability: can you trust the API to accurately detect fake or temporary email addresses without blocking real users from your service?
- Developer experience and API design: is the API well-designed and does it include SDKs for multiple languages?
- Pricing and scalability: does the API include a free tier and does pricing scale predictably and fairly as your needs grow?
Because pricing structure and features vary widely between APIs, we've created a table overview showing the pricing range per verification for each API.
Conclusion
Email verification is a great way to lower your bounce rates and protect your sender reputation. You should verify email addresses before sending to them, and also periodically re-verify your email lists.
The evaluated APIs can provide highly accurate results by validating input, checking MX records, and verifying that the email servers are ready to receive new mail. However, none of these solutions are 100% accurate.
For best results, Resend recommends using email verification APIs alongside other methods. Incorporating CAPTCHAs into signup forms is one safeguard. A confirmation email—for example, a double opt-in setup—is the best way to ensure that the intended user is getting your content. A combination of these methods can lead to higher engagement rates and more reliable deliverability.
Resend can help your emails avoid the spam filter and land in the inbox. View our top 10 deliverability tips.