API reference
One contract for the complete customer surface.
Customer endpoints are available under /api/v1. The legacy /api prefix remains available to the dashboard, while new server integrations should use the versioned base URL.
Authentication boundaries
Product integrations use a workspace API key, which can also read account usage, analytics, and API-key metadata. Billing changes and API-key creation or revocation require the HTTP-only browser session and are labeled accordingly.
Resources
Emails and threads
Send, retrieve, search, reply, and inspect delivery events.
8 operationsLabels and filing rules
Organize sent and received mail into folders automatically or by hand.
9 operationsDrafts and attachments
Build composer flows with private attachment storage.
10 operationsHosted templates
Draft, render, test, version, publish, and send reusable content.
7 operationsDomains
Provision sender identities and understand DNS verification state.
8 operationsInbound email
Create addresses and work with received conversations.
5 operationsDeliverability
Inspect events, reputation outcomes, and blocked recipients.
8 operationsAccount and billing
Read account usage, analytics, and key metadata with an API key; billing changes and key creation or revocation require a dashboard session.
Error envelope
JSON errors use one predictable envelope. Status codes distinguish invalid input, authentication, missing resources, conflicts, payment requirements, safety blocks, and usage limits.
{
"error": {
"message": "The sender domain is not verified",
"status": 403
}
}Versioning
The date-based API version identifies this contract. Backward-compatible fields can be added within the version. Breaking changes require a new versioned base path and a documented transition.
{
"version": "2026-09-07",
"baseUrl": "https://sendhq.cc/api/v1",
"openapi": "https://sendhq.cc/openapi.json"
}