Lettermint

Lettermint is a European partner providing transactional email services, offering reliable delivery of transactional, broadcast, and inbound emails. Their platform includes SDKs for multiple languages, a CLI, and an MCP server for AI assistants. Lettermint is ISO/IEC 27001:2022 certified and GDPR compliant, ensuring secure and privacy‑focused email communications for developers and businesses across Europe.

Lettermint is profiled on the APIs.io network. Tagged areas include Company, Email, Transactional, API, and European.

The Lettermint catalog on APIs.io includes 1 event-driven AsyncAPI specification.

Lettermint’s developer surface includes changelog, sandbox, authentication, documentation, API reference, getting-started guide, support, and 29 more developer resources.

🌐 Visit website 📡 Profile data on GitHub

53.8/100 developing Agent 42/100 agent ready Full breakdown ↓
scored 2026-10-31 · rubric v0.25.0 · Show this score on your site →

0 APIs

Company Email TransactionalAPIEuropean

Kin Score

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

Composite quality — 53.8/100 · developing

Contract Quality 8.3 / 21

Developer Ergonomics 13.0 / 17

Access Clarity 13.0 / 17

Operational Transparency 6.1 / 11

Contract Governance 0.0 / 10

Discoverability 4.1 / 9

Regulatory Posture 3.8 / 15

Agent readiness — 42/100 · agent ready

Machine-Readable Contract 18 / 18

Agentic Access Contract 0 / 10

Documented Reversibility 0 / 6

MCP Server 0 / 12

Machine-Readable Auth 10 / 10

Idempotency 9 / 9

Stable Error Semantics 0 / 8

Request/Response Examples 0 / 7

Rate-Limit Signaling 0 / 7

Typed Event Surface 6 / 6

Agent Skills 0 / 5

Well-Known Catalog 4 / 4

Consent & Bot Identity 0 / 3

A2A Agent Card 0 / 8

Dry-Run / Simulate Mode 0 / 4

Delegated User Identity 6 / 6

Protected Resource Metadata 5 / 5

Registration Without a Human 6 / 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):

MCP Server +12 pts — deployment.mode + probe verdict on the mcp/ manifest, not the pointer; an unprobed slug falls back to authorship
Agentic Access Contract +10 pts — agentic_access artifact present (x-agentic-access), graded by author
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
Rate-Limit Signaling +7 pts — OpenAPI responses document X-RateLimit-* / RateLimit headers (verified), else a rate_limits artifact or RateLimits link (documented)
Request/Response Examples +7 pts — share of operations carrying request/response examples; else an Examples / Code Samples link

5 more unmet checks in the Agent Readiness table above.

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

Contract Quality scores 39.0 — up to +15.3 composite points
Contract Governance scores 0.0 — up to +12.0 composite points
Operational Transparency scores 55.3 — up to +5.8 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/lettermint/apis.yml: open an issue on github.com/api-evangelist/lettermint 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 →

Pricing Plans 1

Published pricing tiers and plan structures.

Lettermint Plans Pricing

25 plans

PLANS

Event Specifications 1

AsyncAPI definitions for this provider's event-driven and streaming APIs.

Lettermint Webhooks

ASYNCAPI

Security Posture 3

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

Lettermint Authentication

1 scheme

SECURITY

Lettermint Domain Security

TLSv1.3 · HSTS · DNSSEC · DMARC

SECURITY

Lettermint Vulnerability Disclosure

security.txt · contact published

SECURITY

Resources

Get Started 5

Portal, sign-up, and the first successful call

Sandbox

Sandbox

DeveloperPortal

GettingStarted

SignUp

Documentation 2

Reference material describing how the API behaves

Documentation

Documentation

APIReference

APIReference

Agent Surfaces 2

MCP servers, agent skills, and machine-readable catalogs

LLMsTxt

LLMsTxt

WellKnown

WellKnown

Design & Contract 3

Pagination, idempotency, versioning, errors, and events

Webhooks

Webhooks

Idempotency

Idempotency

Conventions

Conventions

Build 3

SDKs, sample code, and the tooling you integrate with

SDKs

SDKs

Packages

Packages

Postman

Postman

Access & Security 8

Authentication, authorization, and security posture

Security

Authentication

SecurityTxt

SecurityTxt

SecurityTxt

SecurityTxt

VulnerabilityDisclosure

VulnerabilityDisclosure

DomainSecurity

DomainSecurity

Scroll for all 8

Operate 5

Status, limits, changes, and where to get help

ChangeLog

StatusPage

Roadmap

ChangeLog

Support

Commercial 4

Pricing, plans, and the legal terms of use

TermsOfService

PrivacyPolicy

Plans

Pricing

Company 2

The organization behind the API

Website

Website

Blog

Blog

Other 2

Properties that don't map to a standard resource type

Hosts

Hosts

Vendors

Vendors

Source (apis.yml)

aid: lettermint
name: Lettermint
image: https://lettermint.co/open-graph.jpg
description: Lettermint is a European partner providing transactional email services, offering reliable delivery of transactional,
  broadcast, and inbound emails. Their platform includes SDKs for multiple languages, a CLI, and an MCP server for AI assistants.
  Lettermint is ISO/IEC 27001:2022 certified and GDPR compliant, ensuring secure and privacy‑focused email communications
  for developers and businesses across Europe.
url: https://raw.githubusercontent.com/api-evangelist/lettermint/refs/heads/main/apis.yml
x-type: company
x-source: harvest:new-submission
x-tier: profiled
x-tier-reason: enrichment pass 2026-10-26 (modular-v1; was harvest)
specificationVersion: '0.20'
created: '2026-10-26'
modified: '2026-10-26'
tags:
- Company
- Email
- Transactional
- API
- European
maintainers:
- FN: Kin Lane
  email: kin@apievangelist.com
- FN: APIs.json
  email: info@apis.io
common:
- type: TermsOfService
  url: https://lettermint.co/terms-of-service
- type: PrivacyPolicy
  url: https://lettermint.co/privacy-policy
- type: Plans
  url: plans/lettermint-plans-pricing.yml
- type: Webhooks
  url: asyncapi/lettermint-webhooks.yml
- type: ChangeLog
  url: changelog/lettermint-changelog.yml
- type: Idempotency
  url: conventions/lettermint-conventions.yml
- type: Conventions
  url: conventions/lettermint-conventions.yml
- type: Sandbox
  url: sandbox/lettermint-sandbox.yml
- type: Security
  url: security/lettermint-vulnerability-disclosure.yml
- type: Authentication
  url: authentication/lettermint-authentication.yml
- type: LLMsTxt
  url: llms/lettermint-llms.txt
- type: SecurityTxt
  url: well-known/lettermint-security.txt
- type: SecurityTxt
  url: well-known/lettermint-emailexpert-security.txt
- type: SecurityTxt
  url: well-known/lettermint-bsky-security.txt
- type: SecurityTxt
  url: well-known/lettermint-app-security.txt
- type: WellKnown
  url: well-known/lettermint-well-known.yml
- type: Hosts
  url: hosts/lettermint-hosts.yml
- type: Vendors
  url: vendors/lettermint-vendors.yml
- type: SDKs
  url: packages/lettermint-packages.yml
- type: Packages
  url: packages/lettermint-packages.yml
- type: StatusPage
  url: https://status.lettermint.co/
- type: Sandbox
  url: https://lettermint.co/roadmap/sandbox
- type: Roadmap
  url: https://lettermint.co/roadmap
- type: DeveloperPortal
  url: https://lettermint.co/for/developers
- type: ChangeLog
  url: https://lettermint.co/changelog
- type: VulnerabilityDisclosure
  url: security/lettermint-vulnerability-disclosure.yml
- type: DomainSecurity
  url: security/lettermint-domain-security.yml
- type: Website
  url: https://lettermint.co/
- type: Documentation
  url: https://lettermint.co/docs
- type: APIReference
  url: https://lettermint.co/docs/api-reference/sending
- type: GettingStarted
  url: https://lettermint.co/docs/quickstart
- type: Support
  url: https://lettermint.co/knowledge-base
- type: Blog
  url: https://lettermint.co/blog
- type: Pricing
  url: https://lettermint.co/pricing
- type: SignUp
  url: https://app.lettermint.co/register
- type: Postman
  url: https://www.postman.com/lettermint/workspace
apis: []
x-submission-probe: 200 2026-10-25
x-enrichment:
  date: '2026-10-26'
  status: enriched
  artifacts_added: 28
  pass: modular-v1
  engine: identity=local,contract=local,surfaces=local,docs=local,regulatory=local

Lettermint API — frequently asked questions

How do I authenticate with the Lettermint API?

Lettermint documents its authentication (1 scheme). The details are profiled on APIs.io as Lettermint Authentication.

How much does the Lettermint API cost?

APIs.io lists 25 pricing plans for Lettermint, with each plan's price, limits and inclusions under Pricing Plans on this page.

Is the Lettermint API ready for AI agents?

Lettermint has a Kin Score of 53.8 out of 100 (developing) and an Agent Readiness score of 42.1 (agent-ready), scored by API Evangelist on 2026-10-31.

Work with this as data

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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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