# Outbound SMS API

The Outbound SMS API lets your application send SMS through DIDWW over
HTTPS. Your application submits messages with the credentials of an
[HTTP OUT trunk](../sms-trunks/http-out/http-out-trunk.html), and DIDWW
reports the result of each message to the trunk's **Callback URL**.

The API follows the [JSON:API specification](https://jsonapi.org/format/)
and supports person-to-person (P2P) and application-to-person (A2P)
messaging. To send SMS over SMPP instead, use an [SMPP ESME trunk](../sms-trunks/smpp-esme/smpp-esme-trunk.html).

## Get started

Create an HTTP OUT trunk, send your first message, then send messages in
bulk.

**Create an HTTP OUT trunk**

Set the Callback URL, allowed IP addresses, and the DID numbers that
the trunk can use as senders.

[Create an HTTP OUT trunk](../sms-trunks/http-out/how-to-guides/create-http-out-trunk.html)

**Send your first SMS with the API**

Submit a single message with cURL and check the result.

[Send your first SMS with the API](send-your-first-sms-with-api.html)

**Send bulk SMS with the API**

Send the same message to up to 1000 destination numbers in one
request.

[Send bulk SMS with the API](send-bulk-sms-with-api.html)

## Explore in Postman

The Outbound SMS API collection in Postman contains ready-to-use requests
for single and bulk SMS, status callback examples, and error examples. Use
the button to fork the collection to your Postman workspace and send requests
with your own trunk credentials. Forking requires signing in to Postman. To
browse the requests without signing in, [view the
collection](https://www.postman.com/didww-api/sms-out-documentation/collection/r8wsm1t/sms-out-documentation).

## Technical references

**Outbound SMS API reference**

Look up authentication, endpoints, request attributes, responses, and
limits.

[Outbound SMS API reference](outbound-sms-api-reference.html)

**Status callbacks and delivery receipts**

Receive the processing result and the final delivery status of each
message.

[Status callbacks and delivery receipts](status-callbacks-and-delivery-receipts.html)

**Outbound SMS errors and status codes**

Look up API errors, processing error codes, and delivery receipt
statuses.

[Outbound SMS errors and status codes](outbound-sms-errors-and-status-codes.html)