---
title: "API reference"
description: "Per-resource REST reference derived from the live OpenAPI spec. Prefer the OpenAPI JSON for full schemas."
url: https://www.unitpost.com/docs/api
section: "API reference"
updated: 2026-07-31
---

# API reference

> Per-resource REST reference derived from the live OpenAPI spec. Prefer the OpenAPI JSON for full schemas.

HTML hub: https://www.unitpost.com/docs/api

- [OpenAPI 3.1 spec](https://www.unitpost.com/api/v1/openapi.json): Full machine-readable contract.

- [Emails](https://www.unitpost.com/docs/api/emails): Send, schedule, retrieve, and cancel transactional email. Send one email or a batch of up to 100, track each message's delivery lifecycle, and pull aggregate deliverability stats for your workspace. ([Markdown](https://www.unitpost.com/docs/api/emails.md))
- [Inbound emails](https://www.unitpost.com/docs/api/inbound-emails): Read email your receiving-enabled domains have received — list messages, retrieve full bodies, and download attachments via short-lived signed URLs. ([Markdown](https://www.unitpost.com/docs/api/inbound-emails.md))
- [Contacts](https://www.unitpost.com/docs/api/contacts): Manage the people you email. Create and update contacts one at a time or import thousands in the background, with standard and custom field values that templates can reference as variables. ([Markdown](https://www.unitpost.com/docs/api/contacts.md))
- [Contact fields](https://www.unitpost.com/docs/api/contact-fields): Define the typed custom attributes (text, number, date, …) your contacts carry — usable in templates as per-recipient variables. ([Markdown](https://www.unitpost.com/docs/api/contact-fields.md))
- [Segments](https://www.unitpost.com/docs/api/segments): Named groups of contacts used to target campaigns. Segments decide who a campaign goes to; topics (below) decide what recipients can opt out of. ([Markdown](https://www.unitpost.com/docs/api/segments.md))
- [Topics](https://www.unitpost.com/docs/api/topics): Subscription categories (e.g. Promotions) recipients can opt out of without leaving your list, independent of segment membership. Scope a campaign to a topic and opted-out contacts are skipped automatically. ([Markdown](https://www.unitpost.com/docs/api/topics.md))
- [Campaigns](https://www.unitpost.com/docs/api/campaigns): One-to-many sends to a segment or an inline recipient list. Draft, validate, schedule, send, pause, resume, and cancel — with a pre-send report that catches problems before anything goes out. ([Markdown](https://www.unitpost.com/docs/api/campaigns.md))
- [Templates](https://www.unitpost.com/docs/api/templates): Reusable email designs in the canonical block-based JSON format the dashboard editor produces, with per-recipient `{{variables}}` filled at send time. ([Markdown](https://www.unitpost.com/docs/api/templates.md))
- [Brand kits](https://www.unitpost.com/docs/api/brand-kits): Read-only Brand Kit profiles (voice, labeled colors, pinned library graphics, core pages) for on-brand template authoring. Writes and URL import stay in the dashboard (Settings → Brand). ([Markdown](https://www.unitpost.com/docs/api/brand-kits.md))
- [Domains](https://www.unitpost.com/docs/api/domains): The domains you send from. Add a domain, publish its DNS records, verify it, and manage its tracking and TLS defaults — sending is blocked until the domain verifies. ([Markdown](https://www.unitpost.com/docs/api/domains.md))
- [Webhooks](https://www.unitpost.com/docs/api/webhooks): Register HTTPS endpoints that receive signed event deliveries (delivered, bounced, opened, clicked, …). The signing secret is returned once on create; verify the signature on every delivery. ([Markdown](https://www.unitpost.com/docs/api/webhooks.md))
- [API keys](https://www.unitpost.com/docs/api/api-keys): Create and revoke the API keys your integrations authenticate with. These endpoints are session-gated (dashboard cookie + `apikeys:manage`) and NOT usable with a Bearer API key. ([Markdown](https://www.unitpost.com/docs/api/api-keys.md))
- [Suppressions](https://www.unitpost.com/docs/api/suppressions): Address-level send blocks — the hard "never email this address" list. Combines engine-written bounce/complaint entries, your own additions, and read-only Unitpost-wide blocks. ([Markdown](https://www.unitpost.com/docs/api/suppressions.md))
- [Usage](https://www.unitpost.com/docs/api/usage): Your workspace's current billing-period usage: emails sent, and on paid plans the dollar sending wallet (monthly allowance, spend, purchased credit, overage) in integer USD cents. ([Markdown](https://www.unitpost.com/docs/api/usage.md))