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.
| API | Free Tier | Rate Limit | Commercial | Attribution | Auth | CORS | Caching | Notable Restrictions |
|---|---|---|---|---|---|---|---|---|
| Mailboxlayer | 100 calls/month | 100 calls/month (free) | ✓ | No | API Key (query parameter) | Yes | Yes | Free plan: HTTP only, basic validation only |
| SendGrid | 100 emails/day | 100 emails/day (free forever plan) | ✓ | No | API Key (header) | No | No | Free tier includes SendGrid branding in emails; limited analytics |
| Guerrilla Mail | Unlimited (disposable email) | Reasonable use expected | ✓ | No | None | Yes | Yes | Disposable emails only; not for persistent mailboxes |
| ImprovMX | 1 domain, 25 aliases | Verify on official docs | ✓ | No | API Key (Basic Auth header) | Yes | Yes | Free plan: 1 domain, 25 aliases, email forwarding only |
| Disify | Unlimited | Reasonable use expected | ✓ | No | None | Yes | Yes | Only checks if email domain is disposable; no full validation |
Last updated: 2026-04