GreatHorn

GreatHorn was a cloud-native email security company founded in 2015 in Waltham, Massachusetts, providing anti-phishing, spear-phishing, business email compromise (BEC), and account-takeover protection for Microsoft 365 and Google Workspace. Backed by Uncork Capital, it was acquired by Hornetsecurity in 2021. As of enrichment (July 2026) the greathorn.com domain returns HTTP 404 (Cloudflare, acquired/retired) and the company publishes no live developer portal, API documentation, or OpenAPI surface. No public API artifacts were found to enrich; this profile is retained as a historical/portfolio record.

GreatHorn is profiled on the APIs.io network. Tagged areas include Company, Email Security, Anti-Phishing, Cloud Email, and Business Email Compromise.

🌐 Visit website 📡 Source on GitHub

6.8/100 minimal ▬ flat Agent 0/100 human only Full breakdown ↓
scored 2026-07-27 · rubric v0.5

0 APIs

CompanyEmail SecurityAnti-PhishingCloud EmailBusiness Email CompromiseMicrosoft 365Google WorkspaceCybersecurity

Kin Score

Kin Score How this is scored →
scored 2026-07-27 · rubric v0.5

Composite quality — 6.8/100 · minimal

Contract Quality 0.0 / 25

Developer Ergonomics 0.0 / 20

Commercial Clarity 0.0 / 20

Operational Transparency 0.0 / 13

Governance 0.0 / 12

Discoverability 6.8 / 10

Agent readiness — 0/100 · human only

Machine-Readable Contract 0 / 18

Agentic Access Contract 0 / 15

MCP Server 0 / 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

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/greathorn: open an issue to ask a question, or submit a pull request to add artifacts. Want it done for you? Prioritized profiling — $2,500 →

Source (apis.yml)

aid: greathorn
accessModel:
  pricing: unknown
  onboarding: unknown
  trial: false
  try_now: false
  public: false
  label: Unknown
  confidence: low
  source: []
  generated: '2026-07-22'
  method: derived
image: https://kinlane-images.s3.amazonaws.com/shared/apis-json/icons/greathorn.png
name: GreatHorn
description: GreatHorn was a cloud-native email security company founded in 2015 in Waltham, Massachusetts, providing anti-phishing,
  spear-phishing, business email compromise (BEC), and account-takeover protection for Microsoft 365 and Google Workspace.
  Backed by Uncork Capital, it was acquired by Hornetsecurity in 2021. As of enrichment (July 2026) the greathorn.com domain
  returns HTTP 404 (Cloudflare, acquired/retired) and the company publishes no live developer portal, API documentation, or
  OpenAPI surface. No public API artifacts were found to enrich; this profile is retained as a historical/portfolio record.
url: https://raw.githubusercontent.com/api-evangelist/greathorn/refs/heads/main/apis.yml
x-type: company
x-source: vc-portfolio
x-backed-by:
- uncork-capital
x-tier: stub
x-tier-reason: portfolio-lead
specificationVersion: '0.20'
created: '2026-07-17'
modified: '2026-07-19'
x-status: acquired
x-acquired-by: hornetsecurity
x-acquired-year: 2021
x-domain-status: '404'
tags:
- Company
- Email Security
- Anti-Phishing
- Cloud Email
- Business Email Compromise
- Microsoft 365
- Google Workspace
- Cybersecurity
apis: []
maintainers:
- FN: Kin Lane
  email: kin@apievangelist.com
- FN: APIs.json
  email: info@apis.io
x-enrichment:
  date: '2026-07-19'
  status: backfilled
  pass: local-v1
  note: backfilled from .gitignore signal + verified work evidence