Email APIs Terms Comparison
Side-by-side comparison of free tiers, rate limits, and usage restrictions for 5 email apis.
Terms of service may change. Always verify with the official API documentation before building production applications.
Where these values come from
CORS is verified by us — we read the Access-Control-Allow-Origin header from a real response (last checked 2026-07-31). Free tier and restrictions marked verified were read from the provider's own pricing page on the date shown, and that page is linked so you can re-check it yourself. Rows marked not verified are ones we could not confirm at the source, so we do not publish a number for them. Pricing and licence terms change without notice — confirm with the provider before you commit. If you spot a value that is out of date, tell us and we will correct it.
| API | Free Tier | Rate Limit | Commercial | Attribution | Auth | CORS | Caching | Notable Restrictions |
|---|---|---|---|---|---|---|---|---|
| Mailboxlayer | 100 calls/month verified 2026-08-01 | 100 calls/month (free) | ✓ | No | API Key (query parameter) | Yes | Yes | Free plan: syntax and typo checks only — no SMTP/MX check, no catch-all detection, no bulk endpoint, no HTTPS |
| SendGrid | Not verified — check the provider | Not verified | ✓ | No | API Key (header) | No | No | Free tier includes SendGrid branding in emails; limited analytics |
| Guerrilla Mail | Not verified — check the provider | Not verified | ✓ | No | None | Yes | Yes | Disposable emails only; not for persistent mailboxes |
| ImprovMX | 1 domain, 25 aliases verified 2026-08-01 | Verify on official docs | ✓ | No | API Key (Basic Auth header) | Yes | Yes | Free plan: 1 domain, 25 aliases, email forwarding only |
| Disify | Not verified — check the provider | Not verified | ✓ | No | None | Yes | Yes | Only checks if email domain is disposable; no full validation |
Last updated: 2026-04