SendHQ developer documentation
Email infrastructure with explicit outcomes.
Verify a domain, send expected email, receive replies, publish typed templates, and inspect delivery without hiding provider state.
curl https://sendhq.cc/api/v1/emails \
-H "Authorization: Bearer $SENDHQ_API_KEY" \
-H "Content-Type: application/json" \
-H "Idempotency-Key: welcome-user-42" \
-d '{"from":"Acme <hello@example.com>","to":["customer@example.net"],"subject":"Welcome","text":"Your workspace is ready."}'Choose a path
Start with the job you need to ship.
Send expected email
Single requests, batches, replies, attachments, retries, and delivery events.
02Publish reusable templates
Typed variables, optimistic drafts, exact previews, tests, and immutable releases.
03Receive and thread replies
Inbound addresses, retained messages, private attachments, and conversations.
04Connect an AI agent
Run the SendHQ MCP server with Claude Code, Codex, or Claude Desktop: 59 typed tools with safety labels.
Product guides
Follow the full system, not an isolated request.
Quickstart
Create a key, verify a domain, and send a controlled email with a retry-safe request.
Start hereMigrate from Resend
Map Resend HTTP sends to SendHQ and account for the compatibility boundaries before cutover.
Start hereAuthentication
Use server-side API keys for product integrations and browser sessions for workspace administration.
Start hereErrors and retries
Parse the standard JSON error envelope and decide when a retry is safe.
Start hereVersioning and deprecation
Understand major URL versions, compatible additions, deprecation notices, and sunset windows.
SendSending email
Send transactional messages, batches, replies, attachments, and hosted templates safely.
SendDomains and DNS
Provision sender identities and interpret DNS, SES, propagation, and repair states.
SendHosted templates
Create typed drafts, preview exact output, publish immutable releases, and preserve send provenance.
ReceiveInbound email
Create inboxes, receive routed messages, retain attachments, and build chronological conversations.
ReceiveLabels and buckets
File sent and received mail into labels automatically, and give an agent a bucket its conversations never leave.
ReceiveSpam, updates, and importance
How SendHQ sorts received mail into primary, updates, and spam, flags important messages, and learns from corrections.
OperateDeliverability
Understand provider events, sender-identity reputation, daily ramping, and automatic recovery.
OperateSuppressions and opt-outs
Prevent unsafe delivery to bounced, complained, or unsubscribed recipients.
OperateBilling and limits
Understand trial restrictions, recipient credits, attachment transfer, and webhook-driven entitlements.
ToolsCommand-line interface
Install the SendHQ CLI to send and read email, verify domains, manage inboxes and templates, and run the MCP server from a terminal, a script, or CI.
IntegrationsSupabase Auth emails
Send Supabase sign-up, magic link, password reset, and email change messages through SendHQ with Supabase's Send Email hook and an Edge Function.