Email on Acid

Email on Acid (now branded as Mailgun Inspect) is an email testing and pre-deployment quality assurance platform with a REST API for rendering email previews across 100+ email clients and devices, checking accessibility compliance (WCAG 2.2), validating HTML/CSS compatibility, running spam filter analysis, and automating pre-send email testing workflows via HTTP Basic Authentication.

Email on Acid publishes 4 APIs on the APIs.io network, including Authentication API, Email Clients API, Email Testing API, and 1 more. Tagged areas include Email Testing, Email Previews, Email Clients, Spam Testing, and Accessibility.

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

Email on Acid’s developer surface includes authentication, documentation, engineering blog, pricing, and 11 more developer resources.

🌐 Visit website 📡 Source on GitHub

54.7/100 developing ▬ flat Agent 34/100 agent aware Full breakdown ↓
scored 2026-07-28 · rubric v0.6

AccessPaidSelf serve

4 APIs

Email TestingEmail PreviewsEmail ClientsSpam TestingAccessibilityHTML ValidationEmail Quality AssurancePre-Deployment Testing

Kin Score

Kin Score How this is scored →
scored 2026-07-28 · rubric v0.6

Composite quality — 54.7/100 · developing

Contract Quality 17.5 / 25

Developer Ergonomics 4.3 / 20

Commercial Clarity 11.6 / 20

Operational Transparency 6.8 / 13

Governance 7.0 / 12

Discoverability 7.4 / 10

Agent readiness — 34/100 · agent aware

Machine-Readable Contract 18 / 18

Agentic Access Contract 10 / 10

MCP Server 0 / 12

Machine-Readable Auth 10 / 10

Idempotency 0 / 9

Stable Error Semantics 0 / 8

Request/Response Examples 7 / 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

Improve this rating by publishing the missing artifacts — every area above can be raised, and the full rubric is at apis.io/rating/. This rating is computed from github.com/api-evangelist/email-on-acid: open an issue to ask a question, or submit a pull request to add artifacts. Want it done for you? Prioritized profiling — $2,500 →

APIs 4

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

Rate Limits 1

Documented rate limits and quota policies.

Email On Acid Rate Limits

4 limits

RATE LIMITS

FinOps 1

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

JSON Schema 3

Standalone JSON Schema definitions for this provider's data models.

Examples 4

Example request and response payloads for these APIs.

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

GitHubOrg

GitHubOrg

Access & Security 3

Authentication, authorization, and security posture

TrustCenter

TrustCenter

DomainSecurity

DomainSecurity

Authentication

Authentication

Operate 2

Status, limits, changes, and where to get help

StatusPage

StatusPage

RateLimits

RateLimits

Commercial 3

Pricing, plans, and the legal terms of use

Pricing

Pricing

Plans

Plans

FinOps

FinOps

Company 3

The organization behind the API

Website

Website

LinkedIn

Blog

Blog

Other 1

Properties that don't map to a standard resource type

Source (apis.yml)

name: Email on Acid
description: Email on Acid (now branded as Mailgun Inspect) is an email testing and pre-deployment quality assurance platform
  with a REST API for rendering email previews across 100+ email clients and devices, checking accessibility compliance (WCAG
  2.2), validating HTML/CSS compatibility, running spam filter analysis, and automating pre-send email testing workflows via
  HTTP Basic Authentication.
accessModel:
  pricing: paid
  onboarding: self-serve
  trial: false
  try_now: false
  public: false
  label: Paid · Self-serve signup
  confidence: high
  source:
  - plans
  - authentication
  generated: '2026-07-22'
  method: derived
image: https://kinlane-images.s3.amazonaws.com/shared/apis-json/icons/email-on-acid.png
url: https://raw.githubusercontent.com/api-evangelist/email-on-acid/refs/heads/main/apis.yml
created: '2026-06-13'
modified: '2026-06-13'
specificationVersion: '0.19'
aid: email-on-acid
type: Index
tags:
- Email Testing
- Email Previews
- Email Clients
- Spam Testing
- Accessibility
- HTML Validation
- Email Quality Assurance
- Pre-Deployment Testing
apis:
- aid: email-on-acid:email-on-acid-authentication-api
  name: Email on Acid Authentication API
  description: Verify API credentials
  humanURL: https://api.emailonacid.com/docs/latest
  baseURL: https://api.emailonacid.com/v5
  tags:
  - Authentication
  properties:
  - type: OpenAPI
    url: openapi/email-on-acid-authentication-api-openapi.yml
  - type: Documentation
    url: https://api.emailonacid.com/docs/latest
- aid: email-on-acid:email-on-acid-email-clients-api
  name: Email on Acid Email Clients API
  description: Manage email client lists and defaults for testing
  humanURL: https://api.emailonacid.com/docs/latest
  baseURL: https://api.emailonacid.com/v5
  tags:
  - Email Clients
  properties:
  - type: OpenAPI
    url: openapi/email-on-acid-email-clients-api-openapi.yml
  - type: Documentation
    url: https://api.emailonacid.com/docs/latest
- aid: email-on-acid:email-on-acid-email-testing-api
  name: Email on Acid Email Testing API
  description: Create and manage email rendering tests
  humanURL: https://api.emailonacid.com/docs/latest
  baseURL: https://api.emailonacid.com/v5
  tags:
  - Email Testing
  properties:
  - type: OpenAPI
    url: openapi/email-on-acid-email-testing-api-openapi.yml
  - type: Documentation
    url: https://api.emailonacid.com/docs/latest
- aid: email-on-acid:email-on-acid-spam-testing-api
  name: Email on Acid Spam Testing API
  description: Standalone spam filter analysis and seed list management
  humanURL: https://api.emailonacid.com/docs/latest
  baseURL: https://api.emailonacid.com/v5
  tags:
  - Spam Testing
  properties:
  - type: OpenAPI
    url: openapi/email-on-acid-spam-testing-api-openapi.yml
  - type: Documentation
    url: https://api.emailonacid.com/docs/latest
common:
- type: AgenticAccess
  url: agentic-access/email-on-acid-agentic-access.yml
- type: TrustCenter
  url: security/email-on-acid-trust-center.yml
- type: DomainSecurity
  url: security/email-on-acid-domain-security.yml
- type: Authentication
  url: authentication/email-on-acid-authentication.yml
- type: Website
  url: https://www.emailonacid.com
- type: Documentation
  url: https://api.emailonacid.com/docs/latest
- type: GitHubOrg
  url: https://github.com/emailonacid
- type: LinkedIn
  url: https://www.linkedin.com/company/email-on-acid
- type: Blog
  url: https://www.emailonacid.com/blog/
- type: Pricing
  url: https://www.emailonacid.com/pricing/
- type: StatusPage
  url: https://status.emailonacid.com/
- type: X
  url: https://twitter.com/EmailOnAcid
- type: Plans
  url: plans/email-on-acid-plans-pricing.yml
- type: RateLimits
  url: rate-limits/email-on-acid-rate-limits.yml
- type: FinOps
  url: finops/email-on-acid-finops.yml
maintainers:
- FN: Kin Lane
  email: kin@apievangelist.com