An email validation API checks an address before you accept it: is it typed correctly, does the domain exist, is it a throwaway inbox? Put one behind a contact form or sign-up page and you get fewer bounced replies and less junk in your list.
Below I explain what these checks can and can’t tell you, then list every free email, phone, and address validation API on the public-apis list.
This post is part of my free API series. The full list of categories is in the free API directory.
What an email validation API actually checks
- Format: is it shaped like an email address at all?
- Domain: does the part after the @ exist and accept mail?
- Throwaway inboxes: is it a temporary address that disappears in an hour?
- Typos: did someone type “gmial.com” when they meant “gmail.com”?
- Role addresses: is it a shared inbox like info@ or sales@?
What it can’t do is promise a real person reads that inbox. Treat the result as a helpful signal, not a verdict.
Where validation helps on a small business site
The most useful spot is the contact form. A gentle “did you mean gmail.com?” catches honest typos before you’re left trying to reply to an address that doesn’t exist. It’s also useful on newsletter sign-ups and anywhere you’ll send a receipt or appointment reminder.
Validation doesn’t replace spam protection. It works alongside it. And if your own replies are landing in spam, the problem is usually your domain’s email settings, which I cover in using email on your own domain.
How to choose an email validation API
- Decide how strict to be. Blocking every role address or unusual domain can turn away real customers. Warning is often better than blocking.
- Mind privacy. You’re sending someone’s email address to another company. Pick a provider with a clear privacy policy, and mention form processing in yours.
- Check it on the server. A check that only runs in the browser is easy to skip. Do the real check where the form is received.
- Don’t slow the form down. If the service is slow or down, let the message through rather than losing a customer.
Phone and address checks
The same idea works for phone numbers (is it a real, reachable number, and is it a mobile?) and US street addresses (does it exist, and what’s the full ZIP+4?). These are handy before sending text reminders or shipping anything.
Every validation API on the list
Each entry says whether you need a key. “No key needed” means you can try it right away. “Sign up for a key” means a free account first, and many of those have paid tiers once you grow. “Users connect their own account” means each person signs in with that service. The APIs come from the community-kept public-apis list, and the descriptions are mine. Services change, so check each one before you rely on it.
Check an email address before you accept it
These look for typos, fake domains, and throwaway addresses. Good for contact forms and sign-ups.
- Cloudmersive Validate: A validation toolbox: checks email addresses, phone numbers, VAT numbers, and domain names from one account. Sign up for a key.
- Disify: A free check for whether an email address is shaped correctly and whether it comes from a throwaway inbox service. No key needed. No key needed.
- Email Validation: Abstract API’s email check: format, domain, whether the mailbox is likely deliverable, and whether it’s a free or disposable address. Sign up for a key.
- Email Validator by LifeStep: Checks an email’s format and that its domain accepts mail, flags throwaway and shared (info@) addresses, and suggests typo fixes like gmial.com to gmail.com. No key needed.
- EVA: A small, free email address checker for format and domain. No key needed.
- Kickbox: Kickbox’s free open check tells you whether an email address comes from a disposable inbox service. Kickbox also sells full verification. No key needed.
- Kiprio Email Validate: A free email check for format, whether the domain accepts mail, and throwaway addresses. Sign up for a key.
- mailboxlayer: Checks an email’s format, domain, and mailbox, and flags free, disposable, and shared addresses, from the APILayer family. Sign up for a key.
- MailboxValidator: Checks whether an email address is valid and deliverable, with a free plan for light use. Sign up for a key.
- MailCheck.ai: Blocks sign-ups from temporary email addresses. No key needed. No key needed.
- RankFabrik Verify: Email checks for format, deliverability, and throwaway addresses. Sign up for a key.
- uchecker: Checks large batches of email addresses and shows the mail server’s actual responses. Sign up for a key.
- Verifier: Checks whether an email address is real and able to receive mail. Sign up for a key.
Check your own email setup
Tools that test whether your domain is set up so your mail gets delivered.
- AGPC Domain Check: Grades your domain’s email setup (SPF, DKIM, DMARC, and MX records) and gives you a report you can share. A good first check when your emails land in spam. No key needed.
- Email Spam Tester: Send it a test message and it scores how spammy it looks across dozens of checks, with a plan to fix what it finds. No key needed.
Send email from a website or app
- Atomic Mail: Creates email inboxes that software (like AI assistants) can send and receive from. Sign up for a key.
- EmailJS: Sends email straight from a website’s contact form without your own mail server. Popular for simple static sites. Sign up for a key.
- ImprovMX: Free email forwarding for your own domain, so hello@yourbusiness.com lands in the inbox you already use. The API lets you manage those forwards. Sign up for a key.
- Mailtrap: Sends transactional email (receipts, password resets) and gives you a safe test inbox to preview emails before real customers see them. Sign up for a key.
- PostStack: A Europe-hosted service for transactional and marketing email, with contact lists, broadcasts, and stats. Sign up for a key.
- Sendgrid: One of the best-known services for sending email from websites and apps, such as receipts, notifications, and newsletters, without running your own mail server. Sign up for a key.
- Sendinblue: Now called Brevo: email marketing, transactional email, and text messages from one account. Sign up for a key.
- SendRaven: Email sending built for AI assistants, with reply threads, sending limits, and approval steps. Sign up for a key.
- SMTPfast: Transactional email plus contact lists and broadcasts, with a free monthly allowance. Sign up for a key.
Test inboxes for developers
Throwaway inboxes for testing sign-up flows. Not for real customer mail.
- Best Temp Mail: Disposable inboxes for testing sign-up emails, and it can pull out one-time codes automatically. No key needed.
- DropMail: Creates short-lived inboxes on demand for testing. No key needed.
- Guerrilla Mail: A long-running disposable email service with an API for creating throwaway inboxes. No key needed.
- inboxsink: Test inboxes that wait for an email to arrive and grab the one-time code, for automated sign-up tests. Sign up for a key.
- mail.gw: A “10-minute mail” style throwaway inbox service with an API. No key needed.
- mail.tm: A temporary email service with an API for creating and reading throwaway inboxes. No key needed.
- Mailfornet: Disposable inboxes for automated sign-up tests, with notifications when mail arrives. Sign up for a key.
- Xeramail Temp Mail: Temporary email addresses for privacy and testing, with one-time code extraction. Sign up for a key.
Check a phone number
- Cloudmersive Validate: A validation toolbox: checks email addresses, phone numbers, VAT numbers, and domain names from one account. Sign up for a key.
- Numlookup: Checks whether a phone number is valid anywhere in the world and tells you the carrier and line type. Sign up for a key.
- Numverify: Checks international phone numbers and returns the country, location, carrier, and whether it’s a mobile or landline. Sign up for a key.
- Phone Specification: Specs for phone models: screen, camera, battery, and more. Useful for comparison sites, not for checking numbers. No key needed.
- Phone Validation: Abstract API’s phone check: whether a number is valid, its country, carrier, and line type. Sign up for a key.
- Veriphone: Phone number checks with carrier and line type, and it formats numbers consistently. Sign up for a key.
- VeriRoute Intel: For North American numbers: caller ID name, carrier, and a spam score. Useful before calling back or texting a lead. Sign up for a key.
Check a street address
- Lob.com: US address verification from Lob, which also prints and mails letters and postcards. It confirms an address exists and standardizes it. Sign up for a key.
- RevAddress: Standardizes US addresses and adds congressional and state legislative districts plus census data. Sign up for a key.
- sthan.io Address Parser: Splits a messy, typed-in US address into clean parts: house number, street, unit, city, state, and ZIP. Sign up for a key.
- sthan.io Address Verification: Checks and standardizes US addresses, adds ZIP+4, and says whether mail can be delivered there. Sign up for a key.
- US Autocomplete: Smarty’s address suggestions as someone types, so they pick a real address instead of mistyping one. Sign up for a key.
- US Extract: Finds US mailing addresses inside any block of text, like an email, and pulls them out. Sign up for a key.
- US Street Address: Smarty’s US address verification: confirms the address exists, standardizes it, and adds ZIP+4 and location details. Sign up for a key.
Other checks for forms
- PurgoMalum: A free profanity filter. Send it text and it flags or masks swear words. Handy for reviews, comments, and name fields. No key needed.
- VerifNow: Checks emails, phone numbers, bank account numbers (IBANs), EU VAT numbers, and some national ID formats from one service. Sign up for a key.
Questions I hear a lot
Is there a free email validation API?
Yes. Several on this list need no key, such as Disify, Kickbox, and Email Validator by LifeStep. Paid services usually add deeper checks and higher limits.
Can an API tell me if an email address is real?
It can tell you the format is right, the domain accepts mail, and the address isn’t a known throwaway. It can’t guarantee a person reads it.
Should I block disposable email addresses?
For free trials or sign-ups, often yes. For a plain contact form, a friendly warning is usually enough, since some real people use them for privacy.
Does email validation stop form spam?
Not on its own. Spam bots often use real-looking addresses. Pair validation with a spam filter on the form.
If you’d like a hand
Picking an API and wiring it into a website or small app safely is part of my apps and platforms work. If your contact form collects bad addresses or too much spam, a free website check is an easy place to start.