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.

Mailosaur publishes 7 API contracts indexed on the APIs.io network, including Analysis API, Devices API, Files API, and 4 more. Tagged areas include Email Testing, SMS Testing, Developer Tools, QA Automation, and CI/CD.

The Mailosaur catalog on APIs.io includes 1 JSON-LD context and 1 Spectral governance ruleset.

Mailosaur’s developer surface includes authentication, documentation, engineering blog, pricing, CLI, code examples, API reference, and 41 more developer resources.

🌐 Visit website 📡 Profile data on GitHub

69.3/100 exemplar ▬ flat Agent 26/100 agent aware Front door AI 1/6 silent Heartbeat 68/100 slowing saas Full breakdown ↓
scored 2026-11-06 · rubric v0.27.0 · Show this score on your site →

AccessPaid

1 published contract 5 Agent Skills

Email Testing SMS Testing Developer Tools QA Automation CI/CD SMTP TOTP Deliverability

What this lets a business do 1

Business capabilities this provider's published APIs can perform, derived from its own contracts. Browse all capabilities →

Software Product Engineering Management

BC-4200

AnalysisMessagesServers

GET /api/analysis/spam/{messageId} GET /api/analysis/deliverability/{messageId} POST /api/messages/search POST /api/messages/{messageId}/screenshots

What people ask Mailosaur 7

The questions people put to an LLM, and the jobs they hand an agent, that Mailosaur's APIs answer — each one linked to the operation that does it. Generated by API Evangelist

Mailosaur Messages API List messages in an inbox “Which emails arrived in my test inbox in the last hour?” Create and send a test email “How do I send an email from my test inbox to trigger a workflow in my product?” Delete every message in an inbox “How do I clear out all emails from a test inbox before a test run?” Search for or wait on matching messages “How do I find the email sent to a specific address in my test inbox?”

Mailosaur Servers API List inboxes “Which test inboxes do I have on my account?” Create a new inbox “How do I set up a new test inbox for my QA team?” Get an inbox's details “What settings and user access does a specific inbox have?” Rename an inbox or change its users “How do I rename an existing inbox?”

Mailosaur Devices API List virtual security devices “Which virtual MFA devices have I set up for testing?” Create a virtual security device “How do I save a virtual authenticator device to test two-factor logins?” Delete a virtual security device “How do I remove a virtual security device I no longer need?” Get the current code from a saved device “What is the current one-time password for my saved virtual device?”

Mailosaur Files API Download an email attachment “How do I download a file attached to a test email?” Download an email as an EML file “Can I export a captured email as a raw .eml file?” Download an email client preview screenshot “How do I download the screenshot of my email rendered in a real email client?”

Mailosaur Usage API Check account usage limits “How close is my account to its email and SMS limits?” Review recent usage transactions “What usage did my account rack up over the past month?”

Mailosaur Analysis API Check a test email for spam “Will my email be flagged as spam by filters?” Get a deliverability report for an email “How can I tell if my email will actually reach recipients' inboxes?”

Mailosaur Previews API List email clients available for previews “Which email clients can I render my email previews in?”

Kin Score

Kin Score How this is scored →
scored 2026-11-06 · rubric v0.27.0

Composite quality — 69.3/100 · exemplar

Contract Quality 11.1 / 19

Developer Ergonomics 11.3 / 15

Access Clarity 15.0 / 15

Operational Transparency 5.1 / 10

Contract Governance 2.9 / 9

Discoverability 5.5 / 8

Regulatory Posture 4.4 / 15

Create-or-Update Ergonomics 0.0 / 10

Agent readiness — 26/100 · 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 7 / 7

Rate-Limit Signaling 7 / 7

Typed Event Surface 0 / 6

Agent Skills 5 / 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
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
Registration Without a Human +6 pts — a `registration_endpoint` in the served RFC 8414 / OIDC discovery document
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)
Typed Event Surface +6 pts — AsyncAPI document, OR webhooks/callbacks objects in the as-published OpenAPI, OR common[].type includes Webhooks

7 more unmet checks in the Agent Readiness table above.

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

Contract Quality scores 59.1 — up to +10.2 composite points
Contract Governance scores 31.8 — up to +8.2 composite points
Operational Transparency scores 52.6 — up to +6.2 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/mailosaur/apis.yml: open an issue on github.com/api-evangelist/mailosaur 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 7

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

Plan	Price
personal	From $20 per month , billed annually Includes: Includes 1 user, with support for up to 3 users; 1 inbox (with unlimited email addresses); From 15,0
core	From $50 per month , billed annually Includes: 5 seats included; multiple inboxes; From 75,000 inbound emails/month; SMS and authentication from $3
enterprise	Custom Includes: Custom users, custom inboxes, SSO, SCIM, advanced support & SLAs

Plan details, limits and sources →

Billed by: subscription · FinOps profile →

Pricing Plans 2

Published pricing tiers and plan structures.

Mailosaur Plans Pricing

3 plans

PLANS

Mailosaur Price Estimates

0 plans

PLANS

Rate Limits 1

Documented rate limits and quota policies.

Mailosaur Rate Limits

4 limits

RATE LIMITS

Service Levels 1

Uptime the provider promises or reports, as SLA4OAI. Read from its own pages; APIs.io runs no monitors.

Mailosaur

SLA

FinOps 1

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

Mailosaur Finops

FINOPS

Semantic Vocabularies 1

JSON-LD contexts and semantic vocabularies used across these APIs.

Mailosaur Context

38 classes · 7 properties

JSON-LD

Spectral Rules 1

Spectral governance rulesets for linting and validating these APIs.

Mailosaur — jsonschema rules

6 rules · 4 warnings 2 info

SPECTRAL

4 properties

JSON SCHEMA

Examples 4

Example request and response payloads for these APIs.

Mailosaur Create Server Example

3 fields

EXAMPLE

Mailosaur Deliverability Report Example

3 fields

EXAMPLE

Mailosaur Get Otp Example

3 fields

EXAMPLE

Mailosaur Search Messages Example

3 fields

EXAMPLE

Security Posture 3

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

Mailosaur Authentication

http · 1 scheme

SECURITY

Mailosaur Domain Security

TLSv1.3 · HSTS · DMARC

SECURITY

Mailosaur Trust Center

ISO 27001:2022, PCI DSS, GDPR, UK Data Protection Act, CCPA

SECURITY

Agentic Access 1

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

Mailosaur Agentic Access

28 operations · 12 acting

AGENTIC

Resources

Get Started 4

Portal, sign-up, and the first successful call

DeveloperPortal

DeveloperPortal

GettingStarted

GettingStarted

SignUp

SignUp

Login

Documentation 5

Reference material describing how the API behaves

Documentation

JSONSchema

JSONSchema

JSONSchema

APIReference

Agent Surfaces 4

MCP servers, agent skills, and machine-readable catalogs

AgenticAccess

AgenticAccess

X-MCPServerCandidate

X-MCPServerCandidate

AgentSkill

AgentSkill

LLMsTxt

LLMsTxt

Design & Contract 8

Pagination, idempotency, versioning, errors, and events

Conventions

ErrorCatalog

Lifecycle

DataModel

Conformance

Vocabulary

SpectralRules

JSONLDContext

Scroll for all 8

Build 9

SDKs, sample code, and the tooling you integrate with

GitHubOrg

Packages

SDKs

CLI

Examples

Examples

Examples

Examples

Postman

Scroll for all 9

Access & Security 4

Authentication, authorization, and security posture

TrustCenter

DomainSecurity

Authentication

Compliance

Operate 3

Status, limits, changes, and where to get help

StatusPage

StatusPage

RateLimits

RateLimits

Support

Support

Commercial 6

Pricing, plans, and the legal terms of use

Pricing

Plans

FinOps

TermsOfService

PrivacyPolicy

ServiceLevelAgreement

ServiceLevelAgreement

Company 3

The organization behind the API

Website

Website

LinkedIn

Blog

Blog

Other 2

Properties that don't map to a standard resource type

CapabilityMap

CapabilityMap

Source (apis.yml)

aid: mailosaur
name: Mailosaur
description: 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.
type: Index
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: paid
  onboarding: unknown
  trial: false
  try_now: false
  public: false
  label: Paid
  confidence: high
  source:
  - plans
  - authentication
  - rate-limits
  - security
  generated: '2026-11-06'
  method: derived
image: https://kinlane-images.s3.amazonaws.com/shared/apis-json/icons/mailosaur.png
url: https://raw.githubusercontent.com/api-evangelist/mailosaur/refs/heads/main/apis.yml
created: 2026-06-13
modified: 2026-08-14
specificationVersion: '0.23'
tags:
- Email Testing
- SMS Testing
- Developer Tools
- QA Automation
- CI/CD
- SMTP
- TOTP
- Deliverability
apis:
- aid: mailosaur:mailosaur-analysis-api
  name: Mailosaur Analysis API
  description: Operations for analyzing the content and deliverability of an email, including SpamAssassin scoring and per-provider
    deliverability reports.
  humanURL: https://mailosaur.com/docs/api
  baseURL: https://mailosaur.com/api
  tags:
  - Analysis
  properties:
  - type: OpenAPI
    url: openapi/mailosaur-analysis-api-openapi.yml
  - type: Overlay
    url: overlays/mailosaur-analysis-api-overlay.yaml
  - type: Documentation
    url: https://mailosaur.com/docs/api
  - type: PostmanCollection
    url: https://www.postman.com/mailosaur/mailosaur/documentation/6961255-6cc72dff-f576-451a-9023-b82dec84f95d
- aid: mailosaur:mailosaur-devices-api
  name: Mailosaur Devices API
  description: Operations for managing virtual security devices and retrieving their current one-time passwords (OTPs), used
    to automate testing of app-based multi-factor authentication.
  humanURL: https://mailosaur.com/docs/api
  baseURL: https://mailosaur.com/api
  tags:
  - Devices
  properties:
  - type: OpenAPI
    url: openapi/mailosaur-devices-api-openapi.yml
  - type: Overlay
    url: overlays/mailosaur-devices-api-overlay.yaml
  - type: Documentation
    url: https://mailosaur.com/docs/api
  - type: PostmanCollection
    url: https://www.postman.com/mailosaur/mailosaur/documentation/6961255-6cc72dff-f576-451a-9023-b82dec84f95d
- aid: mailosaur:mailosaur-files-api
  name: Mailosaur Files API
  description: Operations for downloading the raw content associated with a message — file attachments, the full EML source
    of an email, and rendered email previews.
  humanURL: https://mailosaur.com/docs/api
  baseURL: https://mailosaur.com/api
  tags:
  - File
  tags_raw:
  - Files
  properties:
  - type: OpenAPI
    url: openapi/mailosaur-files-api-openapi.yml
  - type: Overlay
    url: overlays/mailosaur-files-api-overlay.yaml
  - type: Documentation
    url: https://mailosaur.com/docs/api
  - type: PostmanCollection
    url: https://www.postman.com/mailosaur/mailosaur/documentation/6961255-6cc72dff-f576-451a-9023-b82dec84f95d
- aid: mailosaur:mailosaur-messages-api
  name: Mailosaur Messages API
  description: Operations for finding, retrieving, creating, forwarding, replying to, and deleting the email and SMS messages
    received by your Mailosaur inboxes.
  humanURL: https://mailosaur.com/docs/api
  baseURL: https://mailosaur.com/api
  tags:
  - Message
  tags_raw:
  - Messages
  properties:
  - type: OpenAPI
    url: openapi/mailosaur-messages-api-openapi.yml
  - type: Overlay
    url: overlays/mailosaur-messages-api-overlay.yaml
  - type: Documentation
    url: https://mailosaur.com/docs/api
  - type: PostmanCollection
    url: https://www.postman.com/mailosaur/mailosaur/documentation/6961255-6cc72dff-f576-451a-9023-b82dec84f95d
- aid: mailosaur:mailosaur-previews-api
  name: Mailosaur Previews API
  description: Operations for discovering the email clients available for generating email previews (screenshots of an email
    rendered in real clients).
  humanURL: https://mailosaur.com/docs/api
  baseURL: https://mailosaur.com/api
  tags:
  - Previews
  properties:
  - type: OpenAPI
    url: openapi/mailosaur-previews-api-openapi.yml
  - type: Overlay
    url: overlays/mailosaur-previews-api-overlay.yaml
  - type: Documentation
    url: https://mailosaur.com/docs/api
  - type: PostmanCollection
    url: https://www.postman.com/mailosaur/mailosaur/documentation/6961255-6cc72dff-f576-451a-9023-b82dec84f95d
- aid: mailosaur:mailosaur-servers-api
  name: Mailosaur Servers API
  description: Operations for creating and managing your Mailosaur inboxes (servers). Inboxes group your tests together, each
    with its own domain and SMTP/POP3/IMAP credentials.
  humanURL: https://mailosaur.com/docs/api
  baseURL: https://mailosaur.com/api
  tags:
  - Servers
  properties:
  - type: OpenAPI
    url: openapi/mailosaur-servers-api-openapi.yml
  - type: Overlay
    url: overlays/mailosaur-servers-api-overlay.yaml
  - type: Documentation
    url: https://mailosaur.com/docs/api
  - type: PostmanCollection
    url: https://www.postman.com/mailosaur/mailosaur/documentation/6961255-6cc72dff-f576-451a-9023-b82dec84f95d
- aid: mailosaur:mailosaur-usage-api
  name: Mailosaur Usage API
  description: Operations for inspecting your account's usage limits and recent transactional usage. These endpoints require
    authentication with an account-level API key.
  humanURL: https://mailosaur.com/docs/api
  baseURL: https://mailosaur.com/api
  tags:
  - Usage
  properties:
  - type: OpenAPI
    url: openapi/mailosaur-usage-api-openapi.yml
  - type: Overlay
    url: overlays/mailosaur-usage-api-overlay.yaml
  - type: Documentation
    url: https://mailosaur.com/docs/api
  - type: PostmanCollection
    url: https://www.postman.com/mailosaur/mailosaur/documentation/6961255-6cc72dff-f576-451a-9023-b82dec84f95d
common:
- type: CapabilityMap
  url: capabilities/mailosaur-capability-edges.yml
  name: Mailosaur Business Capability Map
- type: AgenticAccess
  url: agentic-access/mailosaur-agentic-access.yml
- type: TrustCenter
  url: security/mailosaur-trust-center.yml
- type: DomainSecurity
  url: security/mailosaur-domain-security.yml
- type: Authentication
  url: authentication/mailosaur-authentication.yml
- type: Website
  url: https://mailosaur.com
- type: Documentation
  url: https://mailosaur.com/docs
- type: GitHubOrg
  url: https://github.com/mailosaur
- type: LinkedIn
  url: https://www.linkedin.com/company/mailosaur
- type: X
  url: https://x.com/mailosaur
- type: Blog
  url: https://mailosaur.com/blog
- type: Pricing
  url: https://mailosaur.com/pricing
- type: StatusPage
  url: https://status.mailosaur.com
- type: Plans
  url: plans/mailosaur-plans-pricing.yml
- type: RateLimits
  url: rate-limits/mailosaur-rate-limits.yml
- type: FinOps
  url: finops/mailosaur-finops.yml
- type: Packages
  url: packages/mailosaur-packages.yml
- type: SDKs
  url: packages/mailosaur-packages.yml
- type: CLI
  url: cli/mailosaur-cli.yml
- type: X-MCPServerCandidate
  url: mcp/mailosaur-mcp.yml
  note: 'Renamed from MCPServer 2026-09-03 (roadmap#247): the manifest self-describes as status: candidate — a tool list derived
    from the published API contracts, not an existing server. The scorer already read the manifest and reported mcp_server
    correctly; the MCPServer type was crediting the artifact-type surfaces with a server that does not exist.'
- type: AgentSkill
  url: skills/_index.yml
- type: LLMsTxt
  url: llms/mailosaur-llms.txt
- type: Conventions
  url: conventions/mailosaur-conventions.yml
- type: ErrorCatalog
  url: errors/mailosaur-problem-types.yml
- type: Lifecycle
  url: lifecycle/mailosaur-lifecycle.yml
- type: DataModel
  url: data-model/mailosaur-data-model.yml
- type: Conformance
  url: conformance/mailosaur-conformance.yml
- type: Compliance
  url: https://trust.mailosaur.com
- type: Vocabulary
  url: vocabulary/mailosaur-vocabulary.yml
- type: SpectralRules
  url: rules/mailosaur-jsonschema-spectral-rules.yml
- type: JSONLDContext
  url: json-ld/mailosaur-context.jsonld
- type: JSONSchema
  url: json-schema/mailosaur-message.json
- type: JSONSchema
  url: json-schema/mailosaur-server.json
- type: JSONSchema
  url: json-schema/mailosaur-device.json
- type: Examples
  url: examples/mailosaur-search-messages-example.json
- type: Examples
  url: examples/mailosaur-create-server-example.json
- type: Examples
  url: examples/mailosaur-get-otp-example.json
- type: Examples
  url: examples/mailosaur-deliverability-report-example.json
- type: DeveloperPortal
  url: https://mailosaur.com/docs
- type: APIReference
  url: https://mailosaur.com/docs/api
- type: GettingStarted
  url: https://mailosaur.com/docs/email-testing/sending-to-mailosaur
- type: Support
  url: https://mailosaur.com/contact
- type: SignUp
  url: https://mailosaur.com/app/signup
- type: Login
  url: https://mailosaur.com/app/login
- type: TermsOfService
  url: https://mailosaur.com/terms
- type: PrivacyPolicy
  url: https://mailosaur.com/privacy
- type: Postman
  url: https://www.postman.com/mailosaur/mailosaur/documentation/6961255-6cc72dff-f576-451a-9023-b82dec84f95d
- type: ServiceLevelAgreement
  url: https://mailosaur.com/legal/enterprise-sla
maintainers:
- FN: Kin Lane
  email: kin@apievangelist.com
x-enrichment:
  date: '2026-08-14'
  status: enriched
  artifacts_added: 23
  pass: local-v1

Mailosaur API — frequently asked questions

Does Mailosaur have an API?

Yes. APIs.io lists 7 APIs from Mailosaur, including Mailosaur Analysis API, Mailosaur Devices API and Mailosaur Files API, and 4 more.

Is there an OpenAPI specification for the Mailosaur API?

Yes. APIs.io indexes 7 OpenAPI specifications for Mailosaur, each linked for download from this page.

How do I authenticate with the Mailosaur API?

Mailosaur uses bearer-token authentication (http · 1 scheme). The details are profiled on APIs.io as Mailosaur Authentication.

How much does the Mailosaur API cost?

Mailosaur publishes its prices; its personal plan is From $20 per month , billed annually as of 2026-10-28. APIs.io lists 3 pricing plans for Mailosaur, with each plan's price, limits and inclusions under Pricing on this page.

Is the Mailosaur API ready for AI agents?

Mailosaur has a Kin Score of 69.3 out of 100 (exemplar) and an Agent Readiness score of 25.5 (agent-aware), scored by API Evangelist on 2026-11-06.

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