Quick answer
Resend documents batch and free contacts as 100 emails per batch; 1,000 marketing contacts on Free. Batch requests do not support attachments.
Verified Aug 22, 2026Official source
Current limits
| Constraint | Current value | Scope | Verified source |
|---|---|---|---|
| batch and free contactsBatch requests do not support attachments. | 100 emails per batch; 1,000 marketing contacts on Free | Free and API batch | ResendAug 22, 2026 |
Why does this limit matter?
A large campaign must be split across batch calls while staying under API rate and plan send quotas.
This value is scoped to Free and API batch; a different plan, runtime, model, endpoint, region, or account can produce a different effective constraint.
What should you check?
- Count recipients, batch calls, contacts, and rate-limit cost before scheduling a campaign.
- 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
- Contact count and sent-message quota measure different things.
- 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.
Related