Every API here is available over the APIs.io API and to AI agents over MCP.
openapi: 3.2.0
info:
title: Groundmail Validation API
version: 0.16.0
description: 'Transactional email API for developers.
Auth: `Authorization: Bearer gm_…` with an API key, or `Bearer gm_oat_…` with an OAuth
access token from the device flow (`groundmail login`). Dashboard session cookies work
for integrations.
Azure managed identity (keyless): an Azure workload can send a Microsoft Entra access
token (a JWT) as the Bearer credential instead of a key. Register the identity''s tenant
ID, object ID and token audience in the dashboard (API keys → Azure managed identity);
it then has the same access options as an API key (scopes, domain limit, tenant).
App-only tokens only. Any authentication failure is the same 401 `unauthorized`.
See https://docs.groundmail.dev/authentication/azure-managed-identity.
Test mode: a test key (`gm_test_…`, `POST /api-keys` with `test: true`) behaves
like a live key, but its sends are never delivered: they are stored with
`test: true`, get simulated events and webhooks (`data.test: true`), and do not
count toward plan limits, the sending ramp, stats or billing. Simulator
addresses (`delivered@`, `bounce@`, `block@`, `complaint@`, `suppressed@`,
`delayed@simulator.groundmail.dev`, plus addressing allowed) produce one outcome
each with any key. See https://docs.groundmail.dev/testing.
Tenants: a platform that sends email for its own customers creates one tenant per
customer (`/tenants`), each with its own domains, suppression list, stats, sending
ramp and pause switch. Name the tenant with `tenant` on sends, domains and
suppressions, or send from a domain the tenant owns. API keys and webhook
endpoints can be limited to tenants. Included on pay as you go and the Dedicated plan;
elsewhere a request that names a tenant gets 403 `tenants_not_enabled`. See
https://docs.groundmail.dev/tenants.
Data retention: sent emails (content and events) and received emails are kept for
your plan''s window, then deleted: 7 days on Free, 30 on Pro, 90 on Scale, up to 365
on Dedicated. Past it, `GET /emails/{id}` and `GET /received-emails/{id}` return
404 `not_found` and lists no longer include them. Aggregate stats
(`GET /deliverability`) are kept. Store webhook events to keep history longer. See
https://docs.groundmail.dev/emails#data-retention.
Scopes: every credential carries scopes (`full`, `emails:send`, `emails:read`,
`domains:read`, `domains:write`, `webhooks:write`, `templates:write`,
`suppressions:write`, `account:read`). Each operation lists the scope it needs under
`x-required-scope` (space-separated: all of them; `a | b`: either); a credential
without it gets 403 `insufficient_scope` with `required_scope`. `full` grants everything; `domains:write` includes `domains:read`.
Legacy `sending` API keys have `emails:send` + `emails:read`.
Production base URL: https://api.groundmail.dev'
servers:
- url: https://api.groundmail.dev
description: Production
tags:
- name: Validation
description: Groundmail validation — check an address before you accept or send to it
paths:
/validate:
post:
operationId: validateEmail
x-required-scope: emails:send | emails:read
summary: Validate an email address
description: 'Groundmail validation for one address, for example on a signup form: syntax,
whether the domain can receive email, disposable and role addresses, recent hard
bounces across Groundmail, and a typo suggestion for common mailbox providers.
Free, and nothing is sent to the address. Rate limit: 120 requests a minute and
5,000 an hour per API key.'
tags:
- Validation
security:
- bearerAuth: []
requestBody:
required: true
content:
application/json:
schema:
$ref: '#/components/schemas/ValidateEmailRequest'
responses:
'200':
description: Verdict for the address
content:
application/json:
schema:
$ref: '#/components/schemas/ValidateEmailResponse'
examples:
typo:
summary: Likely typo
value:
email: ada@gmial.com
domain: gmial.com
verdict: risky
reasons:
- possible_typo
suggestion: ada@gmail.com
disposable: false
role: false
no_mail_server:
summary: Domain takes no email
value:
email: ada@no-mail.example
domain: no-mail.example
verdict: invalid
reasons:
- no_mail_server
suggestion: null
disposable: false
role: false
'400':
description: Missing or malformed `email`
content:
application/json:
schema:
$ref: '#/components/schemas/ErrorResponse'
'401':
description: Missing or invalid API key
content:
application/json:
schema:
$ref: '#/components/schemas/ErrorResponse'
'403':
description: The credential lacks `emails:send` and `emails:read`
content:
application/json:
schema:
$ref: '#/components/schemas/ErrorResponse'
'429':
description: Rate limit for this API key reached (`rate_limited`); see `Retry-After`
content:
application/json:
schema:
$ref: '#/components/schemas/ErrorResponse'
components:
schemas:
ErrorResponse:
type: object
required:
- error
properties:
error:
type: object
required:
- message
properties:
message:
type: string
description: What went wrong, in plain English. Wording can change; branch on `code`.
code:
$ref: '#/components/schemas/ErrorCode'
hint:
type: string
description: 'How to fix the error. Specific to the failure when known (for example a sandbox recipient), otherwise the default for `code`.
'
docs_url:
type: string
format: uri
description: Link to this code on the errors page, `https://docs.groundmail.dev/errors#<code>`.
example: https://docs.groundmail.dev/errors#validation_error
upgrade_url:
type: string
description: 'Dashboard path to upgrade when code is plan_limit or domain_limit. Absent for `daily_ramp_limit`, which upgrading does not lift.
'
required_scope:
type: string
description: 'With `insufficient_scope`: the scope (or space-separated scopes) the operation needs. Also sent as `WWW-Authenticate: Bearer error="insufficient_scope", scope="…"`.
'
details:
description: 'Optional structured details. For send blocks this may include `suppressed` (global suppression list) or `category_unsubscribed` plus `category` and `email_id` (category opt-out). A `daily_ramp_limit` carries `stream` (`transactional` or `product`), `daily_limit` (today''s recipient limit for that stream), `used_today`, `recipients` (in this send), `ramp_stage` and `resets_at` (next 00:00 UTC, ISO 8601), plus `tenant` when the tenant''s own limit refused the send.
'
ErrorCode:
type: string
description: 'Stable, machine-readable error code. Each code is documented at
`https://docs.groundmail.dev/errors#<code>`. New codes may be added;
existing codes keep their meaning.
- `validation_error` (400, 422): the request failed validation, or every recipient is suppressed or opted out (422). Fix the field named in `message`/`details`.
- `unauthorized` (401): missing, malformed or revoked API key. Send `Authorization: Bearer gm_…`.
- `forbidden` (403): the key is valid but the action is not allowed (unverified `from` domain, sandbox send to someone other than the account email, no payment method on file, sending restricted).
- `insufficient_scope` (403): the API key''s scope does not cover this endpoint.
- `domain_not_allowed` (403): the API key is limited to other sending domains than the one in `from`, or `from` is on another tenant''s domain.
- `tenants_not_enabled` (403): the request names a tenant, but tenants are not enabled for this account. They are included on pay as you go and the Dedicated plan.
- `newsletter_not_enabled` (403): the send uses `category: "newsletter"`, but newsletter sending isn''t enabled on this account. Newsletter email is accepted only for approved accounts.
- `not_found` (404): no resource with that id for this team.
- `conflict` (409): the resource already exists or its state blocks the change.
- `plan_limit` (429): the plan''s monthly or daily sending limit was reached. See `upgrade_url`.
- `daily_ramp_limit` (429): the send would go over a new account''s daily ramp-up limit for its stream, or its tenant''s own ramp or daily limit (`details.tenant`). Upgrading does not lift it; wait for `details.resets_at`.
- `domain_limit` (403): the plan''s domain limit was reached. See `upgrade_url`.
- `idempotency_conflict` (409): the `Idempotency-Key` was reused with a different body, or the first request is still running.
- `rate_limited` (429): too many requests. Wait `Retry-After` seconds.
- `timeout` (408): a long-poll (GET /test-inbox/wait) ended before a matching email arrived. Safe to call again.
- `upstream_error` (502, 503, 504, or a passed-through 4xx): the mail server did not accept the request. 502/503 are safe to retry with the same `Idempotency-Key`; 504 means the outcome is unknown.
- `not_configured` (503): the feature is temporarily unavailable.
- `internal_error` (500): unexpected server error. Retry with backoff.
'
enum:
- validation_error
- unauthorized
- forbidden
- insufficient_scope
- not_found
- conflict
- plan_limit
- daily_ramp_limit
- domain_limit
- idempotency_conflict
- rate_limited
- timeout
- upstream_error
- not_configured
- internal_error
- domain_not_allowed
- tenants_not_enabled
- newsletter_not_enabled
ValidateEmailRequest:
type: object
required:
- email
properties:
email:
type: string
maxLength: 320
example: ada@gmial.com
ValidateEmailResponse:
type: object
required:
- email
- domain
- verdict
- reasons
- suggestion
- disposable
- role
properties:
email:
type: string
description: The address as checked (trimmed, lowercased)
domain:
type: string
nullable: true
verdict:
type: string
enum:
- valid
- risky
- invalid
description: '`valid`: nothing wrong found. `risky`: can probably receive email but deserves a second look (disposable, catch-all, likely typo). `invalid`: cannot receive email.
'
reasons:
type: array
description: 'What was found. Invalid: `syntax`, `no_mail_server`, `mailbox_not_found`, `previously_bounced`. Risky: `disposable`, `catch_all`, `possible_typo`. Informational (does not change the verdict): `role`.
'
items:
type: string
enum:
- syntax
- no_mail_server
- mailbox_not_found
- previously_bounced
- disposable
- catch_all
- possible_typo
- role
suggestion:
type: string
nullable: true
description: The address with a likely-mistyped domain corrected, or null
example: ada@gmail.com
disposable:
type: boolean
description: A throwaway-inbox service
role:
type: boolean
description: A team or queue mailbox such as `info@` or `support@`
securitySchemes:
bearerAuth:
type: http
scheme: bearer
description: 'Groundmail API key (`gm_…`), OAuth access token (`gm_oat_…`), or a Microsoft Entra access token from an Azure managed identity registered in the dashboard (keyless; see https://docs.groundmail.dev/authentication/azure-managed-identity). All carry scopes; see the API description.
'