MailPace

MailPace is a fast, privacy-focused transactional email API for developers. It delivers application email - password resets, receipts, notifications - over a simple HTTPS REST API and SMTP, with DKIM-verified sending domains, Ed25519-signed webhooks, and EU-based hosting.

MailPace publishes 4 API contracts indexed on the APIs.io network, including API Tokens API, Domains API, Send API, and 1 more. Tagged areas include Email, Transactional Email, Messaging, SMTP, and Privacy.

The MailPace catalog on APIs.io includes 1 Spectral governance ruleset.

MailPace’s developer surface includes authentication, documentation, and 9 more developer resources.

🌐 Visit website 📡 Profile data on GitHub

26.6/100 thin ▬ flat Agent 24/100 agent aware Front door AI 1/6 silent Heartbeat 98/100 alive saas Full breakdown ↓
scored 2026-11-13 · rubric v0.28.0 · Show this score on your site →

AccessFreeSelf serve⚡ Free to try

1 published contract

Email Transactional Email Messaging SMTP Privacy

Kin Score

Kin Score How this is scored →
scored 2026-11-13 · rubric v0.28.0

Composite quality — 26.6/100 · thin

Contract Quality 9.3 / 19

Developer Ergonomics 4.3 / 15

Access Clarity 0.6 / 15

Operational Transparency 1.2 / 10

Contract Governance 1.2 / 9

Discoverability 5.0 / 8

Regulatory Posture 0.9 / 15

Create-or-Update Ergonomics 0.0 / 10

Agent readiness — 24/100 · agent aware

Machine-Readable Contract 18 / 18

Agentic Access Contract 10 / 10

Documented Reversibility 0 / 6

MCP Server 0 / 12

Machine-Readable Auth 10 / 10

Idempotency 0 / 9

Stable Error Semantics 8 / 8

Request/Response Examples 0 / 7

Rate-Limit Signaling 7 / 7

Typed Event Surface 0 / 6

Agent Skills 0 / 5

Well-Known Catalog 0 / 4

Consent & Bot Identity 0 / 3

A2A Agent Card 0 / 8

Dry-Run / Simulate Mode 0 / 4

Delegated User Identity 0 / 6

Protected Resource Metadata 0 / 5

Registration Without a Human 0 / 6

Agentic Commerce Well-Known Document 0 / 5

Pagination 0 / 5

Distinct Operations 3 / 3

MCP Tool Quality 6 / 6

Regulatory Posture applies to this provider. Its tags matched the Horizontal (data, software, accessibility, platform) regime, so Regulatory Posture carries 15 points of the composite. If this regime is wrong for your business, say so on your provider repo — the applicability map is public and we will correct it.

Create-or-Update Ergonomics applies to this provider. This API accepts writes, so it carries 10 points of the composite. It is scored from the published contracts themselves: whether a caller can create-or-update in one call, whether the write accepts a key the caller already holds, and whether the response says which branch ran. Without that, every write needs a search-and-branch in front of it, and the first time that check is skipped a duplicate record is created. Scored against the observed mean rather than raw — a provider at the catalog average is unchanged by this facet, not penalised by it.

The six quality facets above are damped to 75 points between them, because the conditional facet above carries the other 25. That is why each facet's contribution is shown against a damped maximum: raising a quality facet moves the composite by 75% of its nominal weight, not 100%. The full arithmetic is at apis.io/rating/.

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Agent readiness — checks not met, largest first (exact, from this profile):

MCP Server +12 pts — deployment.mode + probe verdict on the mcp/ manifest, not the pointer; an unprobed slug falls back to authorship Ask about this →
Idempotency +9 pts — OpenAPI mutating operations declare an idempotency key — a header, a request-body property, or a named de-duplication token whose own description says so (verified); else common[].type matches /idempoten/i (documented) Ask about this →
A2A Agent Card +8 pts — a2a/-a2a.yml manifest, graded on conformance.grade against A2A 1.0.0 Ask about this →
Request/Response Examples +7 pts — share of operations carrying request/response examples; else an Examples / Code Samples link Ask about this →
Registration Without a Human +6 pts — a `registration_endpoint` in the served RFC 8414 / OIDC discovery document Ask about this →
Delegated User Identity +6 pts — a served discovery document listing authorization_code in grant_types_supported (served), else an oauth2 authorizationCode flow or openIdConnect declared in an OpenAPI (documented) Ask about this →

9 more unmet checks in the Agent Readiness table above.

Kin Score — facets with the most composite points still available (weight × headroom):

Access Clarity scores 4.3 — up to +19.1 composite points Ask about this →
Developer Ergonomics scores 28.6 — up to +14.3 composite points Ask about this →
Contract Quality scores 49.4 — up to +12.7 composite points Ask about this →

Each check links to what satisfies it. Publish the artifact, or tell us where it already lives, and the score moves on the next scoring run.

Not sure how this applies to your stack? Ask about any one item. Kin Lane reads every question, looks at your profile and your situation, and replies with what a fix would take — scoped to that one area, priced up front, yours whether you ship it or not. Ask a question →

Improve this rating by publishing the missing artifacts — every area above can be raised, and the full rubric is at apis.io/rating/. Every facet and dimension name above is a link: it opens that measurement's own page — what it means, the exact checks that feed it, how the whole catalog distributes on it, and the providers at the top of it. This rating is computed from the provider profile at artifacts.apis.io/mailpace/apis.yml: open an issue on github.com/api-evangelist/mailpace to ask a question or point us at an artifact you publish. Submit an artifact on GitHub — free → Manage your own listing — the Influence plan, $499/mo →

Standards implemented 2

Standards this provider implements or carries. De facto ones are profiled and measured by the API Commons; formal ones come from the standards directory and are linked by the provider's own tags. The evidence column says how each claim was established — not that it was made.

SMTP

tagged — the provider's own APIs.json carries the standard as a tag; implementation not verified

OpenAPI

measured — observed by APIs.io (published)

APIs 4

Individual APIs this provider publishes, each with its own machine-readable definition.

MailPace Webhooks API

Delivers outbound, Ed25519-signed event callbacks (email.queued, email.delivered, email.deferred, email.bounced, email.spam) to your endpoints. Configured per domain in the Mail...

MailPace API Tokens API

Manage per-domain API tokens.

MailPace Domains API

Manage sending domains and DKIM verification.

MailPace Send API

Send transactional email.

Open Collections 4

Open, tool-agnostic API collections (OpenAPI-derived and Bruno).

MailPace API Tokens API

OPEN COLLECTION

MailPace API Tokens Domains API

OPEN COLLECTION

MailPace API Tokens Send API

OPEN COLLECTION

MailPace API

OPEN COLLECTION

MailPace API pricing

Not yet checked against MailPace's own pricing page. Compiled by API Evangelist on 2026-06-20 from mailpace.com/pricing; confirm before you rely on a figure. A free plan or tier is listed.

Plan	Price
Free (on request) free	Free
Pay-as-you-go usage	—

Plan details, limits and sources →

Rate limits

Send Rate: see provider documentation emails
Recipients Per Request: 50 recipients
Message Size: 52428800 bytes

Compiled by API Evangelist, not yet checked against MailPace's documentation. Rate-limit details →

Pricing Plans 1

Published pricing tiers and plan structures.

MailPace Plans Pricing

2 plans

PLANS

Rate Limits 1

Documented rate limits and quota policies.

MailPace Rate Limits

3 limits

RATE LIMITS

FinOps 1

Cost, billing, and metering signals for API financial operations.

MailPace Finops

FINOPS

Spectral Rules 1

Spectral governance rulesets for linting and validating these APIs. Counts are the severity each rule declares, not results of running them.

MailPace API Rules

55 rules · 53 error-severity 1 warn-severity 1 info-severity

SPECTRAL

Security Posture 2

Authentication, domain security, vulnerability disclosure, and trust-center signals.

MailPace Authentication

apiKey · 2 schemes

SECURITY

MailPace Domain Security

TLSv1.3 · HSTS · DMARC

SECURITY

Agentic Access (API Evangelist recommendations) 1

Recommended x-agentic-access execution contracts for AI agents.

MailPace Agentic Access

11 operations · 7 acting · 1 human-in-the-loop

11 operations · 7 acting

AGENTIC

Resources

Documentation 1

Reference material describing how the API behaves

Documentation

Documentation

Agent Surfaces 1

MCP servers, agent skills, and machine-readable catalogs

AgenticAccess

AgenticAccess

Build 1

SDKs, sample code, and the tooling you integrate with

GitHubOrganization

GitHubOrganization

Access & Security 2

Authentication, authorization, and security posture

DomainSecurity

DomainSecurity

Authentication

Authentication

Operate 1

Status, limits, changes, and where to get help

RateLimits

RateLimits

Commercial 2

Pricing, plans, and the legal terms of use

Plans

Plans

FinOps

FinOps

Company 3

The organization behind the API

BlogRSS

BlogRSS

LinkedIn

Website

Website

Source (apis.yml)

aid: mailpace
url: https://raw.githubusercontent.com/api-evangelist/mailpace/refs/heads/main/apis.yml
name: MailPace
kind: company
description: MailPace is a fast, privacy-focused transactional email API for developers. It delivers application email - password
  resets, receipts, notifications - over a simple HTTPS REST API and SMTP, with DKIM-verified sending domains, Ed25519-signed
  webhooks, and EU-based hosting.
deliveryModel:
  model: saas
  open_source: false
  commercial: true
  callable_host: true
  label: Hosted service · you call their endpoint
  confidence: high
  source:
  - openapi
  - pricing
  generated: '2026-08-28'
  method: derived
accessModel:
  pricing: free
  onboarding: self-serve
  trial: false
  try_now: true
  public: false
  gated: none
  gated_source:
  - onboarding
  label: Free · Self-serve signup
  confidence: medium
  source:
  - plans
  - authentication
  - security
  generated: '2026-11-13'
  method: derived
image: https://kinlane-images.s3.amazonaws.com/shared/apis-json/icons/mailpace.png
x-docs-platform: docusaurus
x-docs-platform-confidence: medium
x-docs-platform-checked: 2026-10-03
x-docs-hosting: netlify
tags:
- Email
- Transactional Email
- Messaging
- SMTP
- Privacy
created: '2026-06-20'
modified: '2026-10-06'
specificationVersion: '0.23'
apis:
- aid: mailpace:mailpace-webhooks-api
  name: MailPace Webhooks API
  tags:
  - Webhook
  - Event
  - Ed25519
  tags_raw:
  - Webhooks
  - Events
  - Ed25519
  image: https://kinlane-images.s3.amazonaws.com/shared/apis-json/apis-json-logo.jpg
  humanURL: https://docs.mailpace.com/guide/webhooks/
  baseURL: https://app.mailpace.com/api/v1
  properties:
  - url: https://docs.mailpace.com/guide/webhooks/
    type: Documentation
  - url: review.yml
    type: Review
  description: Delivers outbound, Ed25519-signed event callbacks (email.queued, email.delivered, email.deferred, email.bounced,
    email.spam) to your endpoints. Configured per domain in the MailPace dashboard; the public verification key is exposed
    on the domain object.
- aid: mailpace:mailpace-api-tokens-api
  name: MailPace API Tokens API
  description: Manage per-domain API tokens.
  humanURL: https://docs.mailpace.com/reference/send/
  baseURL: https://app.mailpace.com/api/v1
  tags:
  - API Tokens
  properties:
  - type: OpenAPI
    url: openapi/mailpace-api-tokens-api-openapi.yml
  - type: Documentation
    url: https://docs.mailpace.com/reference/send/
  - type: APIReference
    url: https://docs.mailpace.com/reference/overview/
  - type: Documentation
    url: https://docs.mailpace.com/reference/domains/
- aid: mailpace:mailpace-domains-api
  name: MailPace Domains API
  description: Manage sending domains and DKIM verification.
  humanURL: https://docs.mailpace.com/reference/send/
  baseURL: https://app.mailpace.com/api/v1
  tags:
  - Domains
  properties:
  - type: OpenAPI
    url: openapi/mailpace-domains-api-openapi.yml
  - type: Documentation
    url: https://docs.mailpace.com/reference/send/
  - type: APIReference
    url: https://docs.mailpace.com/reference/overview/
  - type: Documentation
    url: https://docs.mailpace.com/reference/domains/
- aid: mailpace:mailpace-send-api
  name: MailPace Send API
  description: Send transactional email.
  humanURL: https://docs.mailpace.com/reference/send/
  baseURL: https://app.mailpace.com/api/v1
  tags:
  - Send
  properties:
  - type: OpenAPI
    url: openapi/mailpace-send-api-openapi.yml
  - type: Documentation
    url: https://docs.mailpace.com/reference/send/
  - type: APIReference
    url: https://docs.mailpace.com/reference/overview/
  - type: Documentation
    url: https://docs.mailpace.com/reference/domains/
common:
- url: https://mailpace.com/rss.xml
  type: BlogRSS
- type: AgenticAccess
  url: agentic-access/mailpace-agentic-access.yml
- type: DomainSecurity
  url: security/mailpace-domain-security.yml
- type: Authentication
  url: authentication/mailpace-authentication.yml
- type: GitHubOrganization
  url: https://github.com/mailpace
- type: LinkedIn
  url: https://www.linkedin.com/company/mailpace
- type: Website
  url: https://mailpace.com
- type: Documentation
  url: https://docs.mailpace.com
- type: Plans
  url: plans/mailpace-plans-pricing.yml
- type: RateLimits
  url: rate-limits/mailpace-rate-limits.yml
- type: FinOps
  url: finops/mailpace-finops.yml
maintainers:
- FN: Kin Lane
  email: kin@apievangelist.com

MailPace API — frequently asked questions

Does MailPace have an API?

Yes. APIs.io lists 4 APIs from MailPace, including MailPace Webhooks API, MailPace API Tokens API and MailPace Domains API, and 1 more.

Is there an OpenAPI specification for the MailPace API?

Yes. APIs.io indexes 3 OpenAPI specifications for MailPace, each linked for download from this page.

How do I authenticate with the MailPace API?

MailPace uses bearer-token authentication (apiKey · 2 schemes). The details are profiled on APIs.io as MailPace Authentication.

How much does the MailPace API cost?

APIs.io lists 2 pricing plans for MailPace, with each plan's price, limits and inclusions under Pricing on this page.

Is the MailPace API ready for AI agents?

MailPace has a Kin Score of 26.6 out of 100 (thin) and an Agent Readiness score of 24.4 (agent-aware), scored by API Evangelist on 2026-11-13.

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