Posteo

Posteo is a German email service provider focused on privacy, security, and sustainability. It offers ad‑free, encrypted email with strong data protection, green hosting powered by renewable energy, and features such as DANE, OpenPGP, and two‑factor authentication. The service emphasizes user anonymity, no tracking, and transparent policies, positioning itself as a secure alternative to mainstream email providers.

Posteo is profiled on the APIs.io network. Tagged areas include Email, Privacy, Security, Sustainability, and German.

Posteo’s developer surface includes engineering blog, support, documentation, getting-started guide, and 9 more developer resources.

🌐 Visit website 📡 Profile data on GitHub

16.5/100 emerging Agent 3/100 human only Full breakdown ↓
scored 2026-10-31 · rubric v0.25.0 · Show this score on your site →

0 APIs

Email Privacy Security SustainabilityGerman

Kin Score

Kin Score How this is scored →
scored 2026-10-31 · rubric v0.25.0

Composite quality — 16.5/100 · emerging

Contract Quality 0.0 / 21

Developer Ergonomics 6.1 / 17

Access Clarity 3.6 / 17

Operational Transparency 0.6 / 11

Contract Governance 0.0 / 10

Discoverability 3.9 / 9

Regulatory Posture 2.1 / 15

Agent readiness — 3/100 · human only

Machine-Readable Contract 0 / 18

Agentic Access Contract 0 / 10

Documented Reversibility 0 / 6

MCP Server 12 / 12

Machine-Readable Auth 0 / 10

Idempotency 0 / 9

Stable Error Semantics 0 / 8

Request/Response Examples 0 / 7

Rate-Limit Signaling 0 / 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 5 / 5

Distinct Operations 3 / 3

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 could not be measured. We hold no machine-readable contract for this provider to read, so there is nothing to measure a write surface against. Excluded rather than scored zero: never-measured and measured-empty are different facts. Publishing an OpenAPI is what makes this facet — and several others — scorable at all.

The six quality facets above are damped to 85 points between them, because the conditional facet above carries the other 15. That is why each facet's contribution is shown against a damped maximum: raising a quality facet moves the composite by 85% 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):

Machine-Readable Contract +18 pts — api_specs includes an OpenAPI document
Agentic Access Contract +10 pts — agentic_access artifact present (x-agentic-access), graded by author
Machine-Readable Auth +10 pts — a served openid-configuration/oauth-authorization-server carrying `issuer` (served), else the securitySchemes class in the provider OpenAPIs — bound (mutualTLS, DPoP, Signature) > negotiable (oauth2 authorizationCode/clientCredentials, openIdConnect) > bearer (http bearer, apiKey)
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)
A2A Agent Card +8 pts — a2a/-a2a.yml manifest, graded on conformance.grade against A2A 1.0.0
Stable Error Semantics +8 pts — OpenAPI $refs a shared error schema across 4xx/5xx responses (verified), else common[].type includes ErrorCatalog / ErrorCodes / DeclineCodes

12 more unmet checks in the Agent Readiness table above.

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

Contract Quality scores 0.0 — up to +25.0 composite points
Access Clarity scores 21.1 — up to +15.8 composite points
Developer Ergonomics scores 35.7 — up to +12.9 composite points

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.

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/posteo/apis.yml: open an issue on github.com/api-evangelist/posteo 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 →

Security Posture 1

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

Posteo Domain Security

TLSv1.3 · HSTS · DNSSEC · DMARC

SECURITY

Resources

Get Started 1

Portal, sign-up, and the first successful call

GettingStarted

GettingStarted

Documentation 1

Reference material describing how the API behaves

Documentation

Documentation

Build 3

SDKs, sample code, and the tooling you integrate with

SDKs

SDKs

Packages

Packages

GitHubOrganization

GitHubOrganization

Access & Security 1

Authentication, authorization, and security posture

DomainSecurity

DomainSecurity

Operate 1

Status, limits, changes, and where to get help

Support

Support

Commercial 2

Pricing, plans, and the legal terms of use

PrivacyPolicy

PrivacyPolicy

TermsOfService

TermsOfService

Company 3

The organization behind the API

Newsroom

Newsroom

Website

Website

Blog

Blog

Other 1

Properties that don't map to a standard resource type

Hosts

Hosts

Source (apis.yml)

aid: posteo
name: Posteo
description: Posteo is a German email service provider focused on privacy, security, and sustainability. It offers ad‑free,
  encrypted email with strong data protection, green hosting powered by renewable energy, and features such as DANE, OpenPGP,
  and two‑factor authentication. The service emphasizes user anonymity, no tracking, and transparent policies, positioning
  itself as a secure alternative to mainstream email providers.
url: https://raw.githubusercontent.com/api-evangelist/posteo/refs/heads/main/apis.yml
x-type: company
x-source: harvest:new-submission
x-tier: profiled
x-tier-reason: enrichment pass 2026-10-27 (modular-v1; was harvest)
specificationVersion: '0.20'
created: '2026-10-27'
modified: '2026-10-27'
tags:
- Email
- Privacy
- Security
- Sustainability
- German
maintainers:
- FN: Kin Lane
  email: kin@apievangelist.com
- FN: APIs.json
  email: info@apis.io
common:
- type: Hosts
  url: hosts/posteo-hosts.yml
- type: SDKs
  url: packages/posteo-packages.yml
- type: Packages
  url: packages/posteo-packages.yml
- type: Newsroom
  url: https://posteo.de/en/news
- type: GitHubOrganization
  url: https://github.com/posteo
- type: DomainSecurity
  url: security/posteo-domain-security.yml
- type: Website
  url: https://posteo.de/
- type: Blog
  url: https://posteo.de/en/blog
- type: PrivacyPolicy
  url: https://posteo.de/en/site/privacy_policy
- type: TermsOfService
  url: https://posteo.de/en/site/terms
- type: Support
  url: https://posteo.de/en/help
- type: Documentation
  url: https://posteo.de/en/site/about_posteo
- type: GettingStarted
  url: https://posteo.de/en/signup
apis: []
x-submission-probe: 302 https://posteo.de/en, 2026-10-26
x-coverage:
  state: unreadable
  reason: no-machine-readable-spec
  detail: Posteo provides no public API documentation or machine‑readable spec.
  evidence:
  - url: https://posteo.de/en
    status: 200
  checked: '2026-10-27'
x-enrichment:
  date: '2026-10-27'
  status: enriched
  artifacts_added: 9
  pass: modular-v1
  engine: identity=local,contract=local,surfaces=local,docs=local,regulatory=local

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Tools for providers

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find_providersBrowse and filter every provider in the catalog.
get_provider_artifactsEvery artifact this provider publishes, grouped by type.
get_provider_operationsEvery operation across all of their OpenAPIs — one call instead of parsing every spec.
get_provider_toolsEvery MCP tool they ship, with the operation each wraps.
get_provider_evidenceHow each part of their score was established. Free — the basis for a claim should not sit behind it.
get_provider_ratingPRO — composite, band, trend and facet scores.
apis_io_searchSTART HERE — APIs, providers and tags for one query, each with its total.
resolveTurn a domain, URL or GitHub org into the provider it belongs to.
find_cohortsEvery scored population of providers in the catalog.

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