Quick answer
SendGrid documents recipients per mail send request as 1,000. The reply_to_list also has a documented 1,000-entry limit.
Verified Aug 22, 2026Official source
Current limits
| Constraint | Current value | Scope | Verified source |
|---|---|---|---|
| recipients per Mail Send requestThe reply_to_list also has a documented 1,000-entry limit. | 1,000 | Mail Send API | Twilio SendGridAug 22, 2026 |
Why does this limit matter?
Large sends need request batching and careful idempotency to avoid duplicate delivery.
This value is scoped to Mail Send API; a different plan, runtime, model, endpoint, region, or account can produce a different effective constraint.
What should you check?
- Count all personalization recipients and generate a stable batch identifier.
- Confirm the exact plan, model, runtime, endpoint, region, and account that serve the failing workload.
- Record the observed value, response headers or configuration, timestamp, and source without logging secrets.
Important caveats
- Account sending reputation, suppression, and plan allowances remain separate.
- Treat the official source and live account configuration as authoritative if they differ from this verified snapshot.
HyperObserve reports the documented platform constraint. Your application, SDK, gateway, provider, region, or account can impose a lower effective limit.
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