Mailosaur
Mailosaur is an email and SMS testing platform for developers and QA teams. It provides a REST API for creating test inboxes, capturing and retrieving messages, running assertions, performing deliverability analysis, and integrating email and SMS testing into CI/CD pipelines. The platform supports authentication testing (TOTP/2FA), spam analysis, SPF/DKIM/DMARC validation, and connects via SMTP, POP3, and IMAP protocols.
Reference-quality API operations across every facet — a rich contract, published governance, transparent operations, and machine-readable commercial terms.
API Evangelist profiles Mailosaur the way a machine reads it — 30 machine-readable artifacts across 1 API, pulled from the provider's own public surface and indexed so a developer, an analyst, or an AI agent can evaluate it against every other provider on the network.
Every provider in the network is reduced to the same set of machine-readable artifacts — OpenAPI contracts, event specifications, GraphQL schemas, runnable collections, pricing and rate-limit signals, security posture, OAuth scopes, and the agent surfaces (MCP servers and skills) that let software drive the API on its own. We profile them because the interface is the part of a company you can actually inspect: it is a truer signal of what a provider does than any marketing page. From those artifacts we compute the Kin Score — Mailosaur scores 68.8/100 (exemplar), with a separate agent-readiness read of 25/100 (agent aware). The full breakdown is below, followed by every artifact we hold — each card links through to its machine-readable definition on apis.io.
Kin Score
This is the API Evangelist rating — a single, repeatable read computed from the artifacts on this page. Green fill is points earned; the red track is points possible, so every bar shows earned-versus-possible at a glance. Every facet and dimension name is a link: it opens that measurement's page on APIs.io, where the rating runs across the whole catalog — the exact checks that feed it, how every profiled provider distributes on it, and who is at the top of it.
Kin Score
How this is scored →scored 2026-09-08 · rubric v0.20.0
Put this on your own site. The badge is drawn live from Mailosaur's current Kin Score — paste it once and it updates itself every time the score is recomputed. It follows your visitor's light or dark setting, and it links back here so anyone who sees it can read the full breakdown.
<!-- Kin Score · API Evangelist -->
<a href="https://providers.apievangelist.com/providers/mailosaur/"
title="Mailosaur on API Evangelist — API profile and Kin Score">
<img src="https://apis.io/badge/mailosaur.svg"
alt="Mailosaur Kin Score — API readiness rating by API Evangelist" width="150" height="150" loading="lazy">
</a>[](https://providers.apievangelist.com/providers/mailosaur/)<!-- Kin Score · API Evangelist -->
<a href="https://providers.apievangelist.com/providers/mailosaur/"
title="Mailosaur on API Evangelist — API profile and Kin Score">
<img src="https://apis.io/badge/mailosaur/card.svg"
alt="Mailosaur Kin Score — API readiness rating by API Evangelist" width="340" height="120" loading="lazy">
</a>More shapes, themes and sizes → · Score as JSON · How badges work
How we profile Mailosaur
Each block below is one kind of artifact we hold for Mailosaur. For each we say what it is and why it earns a place in the profile, then list every one we've indexed — capped at two rows, scroll within the panel for the rest.
APIs 7
Each API is captured as its own OpenAPI definition — every operation, parameter, and response. This is the single most useful machine-readable description of what an API does, and it's what lets us score, lint, mock, and generate against it without asking the provider for anything.
Individual APIs this provider publishes, each with its own machine-readable definition.
Mailosaur Analysis API
Operations for analyzing the content and deliverability of an email, including SpamAssassin scoring and per-provider deliverability reports.
Mailosaur Devices API
Operations for managing virtual security devices and retrieving their current one-time passwords (OTPs), used to automate testing of app-based multi-factor authentication.
Mailosaur Files API
Operations for downloading the raw content associated with a message — file attachments, the full EML source of an email, and rendered email previews.
Mailosaur Messages API
Operations for finding, retrieving, creating, forwarding, replying to, and deleting the email and SMS messages received by your Mailosaur inboxes.
Mailosaur Previews API
Operations for discovering the email clients available for generating email previews (screenshots of an email rendered in real clients).
Mailosaur Servers API
Operations for creating and managing your Mailosaur inboxes (servers). Inboxes group your tests together, each with its own domain and SMTP/POP3/IMAP credentials.
Mailosaur Usage API
Operations for inspecting your account's usage limits and recent transactional usage. These endpoints require authentication with an account-level API key.
Scroll within the panel for all 7 ·
Open Collections 7
Open, tool-agnostic collections carry the same runnable value as Postman without locking you to one client — the portable, forkable form of the same exercise.
Open, tool-agnostic API collections (OpenAPI-derived and Bruno).
API Collection
OPEN COLLECTIONMailosaur Analysis API
OPEN COLLECTIONMailosaur Analysis Devices API
OPEN COLLECTIONMailosaur Analysis Files API
OPEN COLLECTIONMailosaur Analysis Messages API
OPEN COLLECTIONMailosaur Analysis Servers API
OPEN COLLECTIONMailosaur Analysis Usage API
OPEN COLLECTIONScroll within the panel for all 7 ·
Pricing Plans 1
Pricing is part of the interface. Machine-readable plans tell you what a tier costs and includes before you commit — one of the things the Kin Score reads for access clarity — renamed from commercial clarity in rubric 0.12, because a free statutory interface has access terms and no commercial ones.
Published pricing tiers and plan structures.
Rate Limits 1
Rate limits are the difference between a demo that works and a production integration that doesn't fall over. Publishing them is an operational-transparency signal — and a hard requirement for any agent that plans its own throughput.
Documented rate limits and quota policies.
Mailosaur Rate Limits
RATE LIMITSFinOps 1
Cost, billing, and metering signals let a buyer model the financial operations of an API before it's live. We profile them for the same reason we profile pricing: the money is part of the contract.
Cost, billing, and metering signals for API financial operations.
Mailosaur Finops
FINOPSSemantic Vocabularies 1
JSON-LD contexts give the data shared meaning across APIs. We profile them because semantics are what let a machine reconcile 'customer' here with 'customer' somewhere else.
JSON-LD contexts and semantic vocabularies used across these APIs.
Mailosaur Context
JSON-LDSpectral Rules 1
Governance rulesets we run against this provider's specs — the automated checks behind parts of the score. Profiling them makes the quality bar explicit and re-runnable, not a matter of opinion.
Mailosaur API Rules
SPECTRALJSON Schema 3
Standalone JSON Schema definitions describe the data models behind the API. We profile them so the shapes are validatable on their own — useful long after a single request is forgotten.
Standalone JSON Schema definitions for this provider's data models.
Examples 4
Real request and response payloads are what turn a spec from abstract into obvious — and they're one of the twelve things an agent needs to call an API correctly on the first try.
Example request and response payloads for these APIs.
Security Posture 3
Authentication, domain security, vulnerability disclosure, and trust-center signals — the evidence that a provider takes security seriously enough to document it. We profile it because you can't govern what you can't see.
Authentication, domain security, vulnerability disclosure, and trust-center signals.
Agentic Access 1
An x-agentic-access contract marks which operations are safe for an agent to run on its own and which need a human in the loop. It is the difference between an API an agent can use and one it can use safely.
Recommended x-agentic-access execution contracts for AI agents.
Resources
Every other property we hold for Mailosaur — documentation, portals, status pages, policies, and corporate surface — grouped by the job it does, following the integrator's arc from getting started to running in production.
Get Started 4
Portal, sign-up, and the first successful call
Documentation 5
Reference material describing how the API behaves
Agent Surfaces 4
MCP servers, agent skills, and machine-readable catalogs
Design & Contract 8
Pagination, idempotency, versioning, errors, and events
Scroll within the panel for all 8 ·
Build 9
SDKs, sample code, and the tooling you integrate with
Scroll within the panel for all 9 ·
Access & Security 4
Authentication, authorization, and security posture
Operate 3
Status, limits, changes, and where to get help
Commercial 6
Pricing, plans, and the legal terms of use
Company 3
The organization behind the API
Other 1
Properties that don't map to a standard resource type
← All providers · Data indexed from github.com/api-evangelist/mailosaur · machine-readable index on apis.io
This is an independent, third-party profile of Mailosaur, published by API Evangelist. We do not operate, host, resell, or support these APIs, and we are not affiliated with or endorsed by the company unless stated above. Everything here is built from publicly available information — the company's own site, developer portal, documentation, public repositories, and the specifications it publishes for public use. Nothing is obtained by breaching a system, defeating an access control, or using credentials.
The Kin Score and Agent Readiness rating are independently calculated assessments of a company's public API artifacts, scored against a published rubric. They are not certifications, endorsements, security assessments, or audits.
Corrections, re-scores, and removal are free — no partnership or purchase required, and you do not need to justify the request. A removed company is recorded as unrated, never scored zero for having asked. Acknowledgement within one business day; removal within two.
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