inboxsink API alternatives

Disposable inboxes for end-to-end tests that wait for the email and extract OTP codes. If it doesn't fit your project, here are the 10 best free Email APIs to use instead in 2026, out of 36 in the directory.

For reference, inboxsink API: HTTPS.

1. 1

   Kickbox API

   Online · 1026 ms

   Email verification API. A free email API by Powered by Kickbox.

   • No API key needed
   • Callable from the browser (CORS)
   • HTTPS

   No authHTTPSCORS
2. 2

   mail.gw API

   Online · 546 ms

   API for creating temporary email accounts.

   • No API key needed
   • Callable from the browser (CORS)
   • HTTPS

   No authHTTPSCORS
3. 3

   mail.tm API

   Online · 454 ms

   Temporary Email Service. A free email API by Mail.tm.

   • No API key needed
   • Callable from the browser (CORS)
   • HTTPS

   No authHTTPSCORS
4. 4

   MailSenpai DNS Check API

   Online · 805 ms

   Check a domain's SPF, DKIM, DMARC and MX records and get what to fix, with the values to publish.

   • No API key needed
   • Callable from the browser (CORS)
   • HTTPS

   No authHTTPSCORS
5. 5

   Cloudmersive Validate API

   Online · 622 ms

   Validate email addresses, phone numbers, VAT numbers and domain names.

   • Callable from the browser (CORS)
   • HTTPS

   apiKeyHTTPSCORS
6. 6E

   Email Validator by LifeStep API

   Online · 1178 ms

   Validate email syntax and MX, detect disposable/role addresses, suggest typo fixes.

   • No API key needed
   • Callable from the browser (CORS)
   • HTTPS

   No authHTTPSCORS
7. 7

   EmailJS API

   Online · 505 ms

   Send emails directly from client-side JavaScript without a backend server.

   • Callable from the browser (CORS)
   • HTTPS

   apiKeyHTTPSCORS
8. 8

   Mailfornet API

   Online · 788 ms

   Disposable inboxes for end-to-end signup tests, with long-polling and HMAC-signed webhooks.

   • Callable from the browser (CORS)
   • HTTPS

   apiKeyHTTPSCORS
9. 9

   SMTPfast API

   Online · 783 ms

   Send transactional email, manage contacts and broadcasts, free 3,000 emails/month.

   • Callable from the browser (CORS)
   • HTTPS

   apiKeyHTTPSCORS
10. 10

    Atomic Mail API

    Online · 357 ms

    Email for AI agents: programmatic inbox creation and send/receive over JMAP.

    • Fast: 357 ms response
    • HTTPS

    apiKeyHTTPSCORS ?

inboxsink API vs alternatives

inboxsink API compared with its alternatives

API	API key	HTTPS	CORS	Uptime	Response	Rating
inboxsink	Required	Yes	No	Up	612 ms	Not rated
Kickbox	No	Yes	Yes	Up	1026 ms	Not rated
mail.gw	No	Yes	Yes	Up	546 ms	Not rated
mail.tm	No	Yes	Yes	Up	454 ms	Not rated
MailSenpai DNS Check	No	Yes	Yes	Up	805 ms	Not rated
Cloudmersive Validate	Required	Yes	Yes	Up	622 ms	Not rated
EEmail Validator by LifeStep	No	Yes	Yes	Up	1178 ms	Not rated
EmailJS	Required	Yes	Yes	Up	505 ms	Not rated
Mailfornet	Required	Yes	Yes	Up	788 ms	Not rated

See also: best Email APIs · all Email APIs