OpenSend docs
What sending feature should I use?
OpenSend has several sending surfaces. Choose the one that matches the job instead of forcing every workflow through one endpoint.
| Need | Use | Why |
|---|---|---|
| One transactional message | /emails or an SDK | Fast API response, idempotency support, direct lifecycle record |
| A few transactional messages together | /emails/batch | One request with per-message results |
| A campaign to a list | Broadcasts | Segments, unsubscribe handling, scheduling, and performance review |
| Lifecycle flow | Automations | Trigger, delay, condition, wait, and template steps |
| Legacy app with SMTP only | SMTP relay | Uses API keys and routes through the normal delivery pipeline |
| Generated client in another language | /openapi.json | Exact route and schema contract |
For retries, use idempotency keys. For high-volume marketing, use broadcasts and segments rather than loops over transactional sends.
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More in Knowledge base
This page is intentionally concise. Use the neighboring guides below for the next implementation details, route contracts, or operational steps.
Warming up a sending domain
Warmup is the process of increasing sending volume gradually so mailbox providers can observe consistent, wanted mail from your domain.
What counts as email consent?
Consent means the recipient has a reasonable expectation that your organization will send the type of email they receive. OpenSend provides contacts, topics, unsubscribe pages, and suppressions to help enforce consent, but your team owns the policy and legal interpretation.
Consent, unsubscribes, topics, and suppressions
OpenSend has several related safety concepts. Use them together instead of treating them as one field.
Quotas, rate limits, and production access
OpenSend has application-level rate limits, plan quotas, and provider-side sending limits. Treat them as separate controls.
How to handle API keys
API keys are bearer credentials. Anyone with a valid key can call the OpenSend API within that key's permissions and restrictions.
What attachment types are not supported?
OpenSend accepts attachments through the email API and SMTP relay, but operators should restrict unsafe or oversized files according to their security policy and provider limits.