24 Free Email Tools
for AI Agents & Developers
Every email diagnostic, analysis, and planning tool on EmailCloud is available as a REST API endpoint and MCP tool. Try any tool free — register with your email for continued access. Connect your AI agent or application and start making calls.
Quick Start
Base URL: https://api.emailcloud.com
REST API — Try it now
MCP — Connect your AI agent
Why Connect Your AI Agent to EmailCloud
AI agents that handle email — whether writing campaigns, debugging deliverability, auditing security, or advising marketers — need real-time access to email infrastructure data. EmailCloud provides that data through 24 purpose-built tools.
Real-Time Email Diagnostics
Your agent can check SPF, DMARC, MX, and blacklist status for any domain in milliseconds. No static databases — live DNS queries against authoritative nameservers and 14 major blocklists.
Content Quality Analysis
Grade subject lines on 12 factors, detect 500+ spam trigger words by severity, check Gmail size limits, validate CTA contrast ratios. Give your agent the ability to audit email content before it sends.
Deliverability Intelligence
Full 12-point deliverability testing: send a real email and get back authentication results, spam scoring, blacklist status, header analysis, and content checks — the same analysis enterprise tools charge $79-1,000+/month for.
Planning and Strategy
Warmup schedules, optimal send times, frequency recommendations, ROI projections, and list decay forecasting. Your agent can build data-driven email strategies, not just guess.
Compliance Checking
Check cold email laws for any country-to-country combination. Your agent can verify whether a planned outreach campaign is legal before it launches — across US, EU, UK, Canada, and Australia jurisdictions.
Zero Friction Integration
Try any tool instantly — no signup for your first check. Register with just an email for continued access. MCP-native discovery means compatible AI services can find and use all 24 tools automatically. Your agent is productive in seconds, not days.
All 24 API Tools
Every tool is a single REST endpoint. First check is free — email login required for continued use. JSON in, JSON out.
🔍Deliverability Testing (2 endpoints)
Generate Test Inbox
/api/generate Create a temporary email address for deliverability testing. Send your email to it and get a 12-point analysis.
Get Deliverability Report
/api/results/{email_id} Poll for results after sending a test email. Returns spam score, SPF/DKIM/DMARC validation, blacklist status, content analysis, and more.
🌐DNS and Domain Checks (5 endpoints)
SPF Checker
/api/tools/spf/{domain} Validate any domain's SPF record. Returns the full record, parsed mechanisms, DNS lookup count (max 10), and syntax warnings.
DMARC Checker
/api/tools/dmarc/{domain} Analyze a domain's DMARC policy. Returns policy level, subdomain policy, reporting addresses, alignment settings, and actionable recommendations.
MX Record Lookup
/api/tools/mx/{domain} Look up mail servers for any domain. Returns prioritized MX records and detects the email service provider (Google Workspace, Microsoft 365, Proofpoint, etc.).
Blacklist Checker
/api/tools/blacklist/{target} Check any domain or IP address against 14 major DNS blocklists including Spamhaus, Barracuda, SpamCop, and SORBS. Returns a 0-100 reputation score.
Deliverability Score
/api/tools/deliverability-score/{domain} Get an instant A-F grade on a domain's email authentication setup. Checks SPF, DKIM, DMARC, and MX configuration in one call.
🔧Record Builders (2 endpoints)
SPF Record Builder
/api/tools/spf-builder Generate a valid SPF TXT record. Select your email services and get a complete record ready to paste into DNS.
DMARC Record Generator
/api/tools/dmarc-generator Build a DMARC TXT record with the correct policy, reporting addresses, and alignment settings.
✍️Content Analysis (5 endpoints)
Subject Line Grader
/api/tools/subject-grade Score any subject line on 12 factors: length, power words, spam risk, personalization, numbers, urgency, emoji, word count, action verbs, and mobile fit. Returns A+ through F grade.
A/B Subject Line Tester
/api/tools/ab-test Compare two subject lines side by side. Both get scored on the same 12 factors, with a winner declared and detailed breakdowns for each.
Spam Word Checker
/api/tools/spam-words Scan email copy for spam trigger words. Returns matches color-coded by severity (critical, warning, caution) with safer alternatives suggested for each.
Email Character Counter
/api/tools/character-count Count characters and estimate pixel width for subject lines. Shows how the subject will appear in Gmail, Outlook, and mobile previews.
CTA Contrast Checker
/api/tools/contrast Check WCAG accessibility contrast ratios for email call-to-action buttons. Validates foreground/background color combinations.
📧Headers and Size (2 endpoints)
Email Header Analyzer
/api/tools/headers Parse raw email headers to trace the delivery path, check authentication results (SPF, DKIM, DMARC), identify delays between hops, and detect TLS usage.
HTML Email Size Checker
/api/tools/email-size Check if your email HTML will get clipped by Gmail (102KB limit). Returns total size, whether it exceeds the threshold, and optimization suggestions.
📊Planning Tools (5 endpoints)
Warmup Calculator
/api/tools/warmup Generate a day-by-day email warmup schedule based on domain age, current volume, and target volume. Returns a complete ramp-up plan.
Send Time Optimizer
/api/tools/send-time Find the best day and time to send emails based on industry vertical and audience type. Returns ranked time slots with expected engagement lift.
Email Frequency Calculator
/api/tools/frequency Calculate ideal sending frequency based on list size, industry, and current engagement metrics.
ROI Calculator
/api/tools/roi Calculate email marketing revenue, ROI percentage, and revenue per subscriber from your campaign metrics.
UTM Builder for Email
/api/tools/utm-builder Generate UTM-tagged URLs for tracking email campaigns in Google Analytics. Returns the complete tagged URL ready to use.
📈Analytics (3 endpoints)
Unsubscribe Rate Calculator
/api/tools/unsub-rate Calculate your unsubscribe rate and compare it to industry benchmarks. Flags rates that indicate list health problems.
Revenue Per Subscriber
/api/tools/revenue-per-sub Calculate the dollar value of each subscriber and your total email list valuation.
List Decay Projector
/api/tools/list-decay Project how your email list will grow or shrink over 12 to 36 months based on current growth rate, churn rate, and list hygiene practices.
⚖️Compliance (1 endpoint)
Cold Email Law Checker
/api/tools/cold-email-law Check email marketing laws for any country combination. Returns the applicable law, consent model, specific requirements, penalties, and compliance recommendations.
Account & Meta
POST /api/register Register for a free API key. Optional — enables usage tracking and higher rate limits.
GET /api/health Health check endpoint. Returns service status.
GET /api/stats Public usage statistics. Tests run in the last 24 hours and all time.
Compatible AI Services and Platforms
EmailCloud tools work with any AI service that can make HTTP requests. Services with native MCP support can discover and use all 24 tools automatically. Others connect through their respective function calling, plugin, or tool definition mechanisms.
Native MCP Support — Automatic Discovery
Claude
Anthropic — AI Assistant
Native MCP support. Claude can connect to EmailCloud tools directly through the MCP protocol, enabling real-time email diagnostics within conversations.
Claude Code
Anthropic — AI Code Editor
Native MCP support. Developers using Claude Code can check SPF records, analyze headers, and test deliverability without leaving the editor.
Cursor
Cursor — AI Code Editor
Native MCP support. Add EmailCloud as an MCP server in Cursor settings for inline email tool access during development.
Windsurf
Codeium — AI Code Editor
Native MCP support. Configure the EmailCloud MCP endpoint to access email diagnostic tools alongside your code.
Cline
Open Source — AI Code Editor
Native MCP support. Cline connects to EmailCloud tools for automated email infrastructure checks within VS Code.
GitHub Copilot
GitHub / Microsoft — AI Code Editor
MCP support via extensions. Access EmailCloud tools as Copilot agent extensions for email-related development tasks.
LangChain
LangChain — AI Framework
Native MCP client support plus direct tool definitions. Build email-aware agent chains that check SPF records, analyze spam triggers, and generate warmup schedules.
Dify
Dify — AI Platform
MCP support via tool nodes. Drag-and-drop EmailCloud tools into your Dify workflow for visual email automation pipelines.
Continue
Open Source — AI Code Editor
Native MCP support. Configure EmailCloud as a tool provider for email diagnostics alongside code development in VS Code or JetBrains.
API Compatible — Via Function Calling, Plugins, or HTTP
ChatGPT
OpenAI — AI Assistant
Connect via custom GPT Actions or the Assistants API function calling. Point actions at api.emailcloud.com endpoints for email tool access inside ChatGPT.
Gemini
Google — AI Assistant
Connect via function calling declarations. Define EmailCloud endpoints as tools in Gemini API for automated email analysis.
Copilot
Microsoft — AI Assistant
Integrate via plugins or Semantic Kernel tool definitions. Access EmailCloud tools through the Microsoft AI ecosystem.
Perplexity
Perplexity AI — AI Search
Reference EmailCloud tools in research queries. Perplexity can surface tool results when users ask about email deliverability diagnostics.
Grok
xAI — AI Assistant
Connect via function calling. Define EmailCloud API endpoints as callable tools for email analysis within Grok conversations.
LlamaIndex
LlamaIndex — AI Framework
Define EmailCloud endpoints as tool specs. Build RAG pipelines that incorporate live email diagnostic data from our API.
CrewAI
CrewAI — AI Framework
Assign EmailCloud tools to specialized agents. Create email deliverability audit crews that check authentication, test content, and generate reports.
AutoGPT
Open Source — AI Agent
Register EmailCloud endpoints as plugins. Autonomous agents can monitor email deliverability, check blacklists, and alert on issues.
OpenAI Assistants API
OpenAI — AI Platform
Define EmailCloud tools as function definitions in your assistant. Users can check email authentication, grade subject lines, and analyze headers through your custom assistant.
Amazon Bedrock Agents
AWS — AI Platform
Define EmailCloud endpoints as action groups. Build enterprise email monitoring agents that run deliverability checks on schedules.
Azure AI Agent Service
Microsoft — AI Platform
Configure EmailCloud tools as agent tool definitions. Integrate email diagnostics into Azure-hosted AI workflows.
Google Vertex AI
Google — AI Platform
Define EmailCloud endpoints as function declarations in Vertex AI agents. Automate email infrastructure monitoring at enterprise scale.
Semantic Kernel
Microsoft — AI Framework
Register EmailCloud API endpoints as native functions. Build .NET and Python AI applications with built-in email diagnostic capabilities.
n8n
n8n — Automation
Connect via HTTP request nodes. Build automated email monitoring workflows that check blacklists, validate authentication, and alert your team.
Zapier AI
Zapier — Automation
Connect via webhook actions. Trigger EmailCloud checks automatically when new domains are added, campaigns are scheduled, or alerts fire.
Make
Make (Integromat) — Automation
Connect via HTTP modules. Build visual automation scenarios that incorporate email deliverability checks into your existing workflows.
Flowise
Open Source — AI Framework
Add EmailCloud as a custom tool node. Build drag-and-drop AI chatflows with email diagnostic capabilities.
Haystack
deepset — AI Framework
Define EmailCloud endpoints as pipeline tools. Build NLP pipelines that incorporate email data analysis and deliverability checks.
Using a different AI service or framework?
If your platform can make HTTP requests, it can use EmailCloud tools. The API uses standard REST conventions — GET for lookups, POST with JSON body for analysis tools. No OAuth, no SDK dependency, no complex authentication. Check the endpoint reference above for request formats, or point your AI at our llms.txt file for automatic discovery.
What AI Agents Build With EmailCloud
Email Deliverability Auditor
An agent that takes a domain name, runs SPF + DMARC + MX + blacklist checks, then generates a plain-English report with prioritized fix recommendations. Takes 4 API calls and returns in under 2 seconds.
Email Campaign Pre-Flight Check
Before a campaign sends, the agent grades the subject line, checks for spam trigger words, validates HTML size against Gmail limits, and verifies CTA button contrast meets accessibility standards.
New Domain Setup Assistant
An agent that guides users through setting up email for a new domain: generates the correct SPF record, builds a DMARC policy, creates a warmup schedule, and monitors authentication setup as DNS propagates.
Email Marketing Strategy Bot
A planning agent that calculates ROI projections, recommends send frequency and timing, projects list growth/decay, and generates tracked UTM URLs for campaigns — all from conversation.
Cold Outreach Compliance Checker
Before sending cold emails internationally, the agent verifies the legal requirements for the sender/recipient country combination, checks the sender domain's authentication, and validates the email content for spam triggers.
Email Header Forensics
A debugging agent that parses raw email headers, traces the delivery path hop by hop, identifies authentication failures, finds delivery delays, and cross-references the sending IP against blacklists.
Technical Details
API Conventions
- Base URL: https://api.emailcloud.com
- Format: JSON request and response bodies
- Auth: None required. Optional
X-API-Keyheader for tracked access - GET endpoints: Domain/IP checks — pass the target in the URL path
- POST endpoints: Content analysis and calculators — send JSON body
- CORS: Enabled for emailcloud.com and localhost:4321
- Rate limits: /api/generate: 10/min/IP. All instant tools: unlimited
- Uptime: 99.9%+ on DigitalOcean infrastructure
MCP Protocol
- Manifest:
/.well-known/mcp.json - Protocol: Model Context Protocol (MCP) — open standard by Anthropic
- Transport: HTTP+SSE (Server-Sent Events)
- Tools declared: 24 tools with full input/output schemas
- Discovery: Automatic via manifest URL or
/llms.txt - LLM file:
/llms.txton both api.emailcloud.com and emailcloud.com - Supported clients: Claude, Cursor, Windsurf, Cline, Continue, LangChain, Dify, GitHub Copilot
- No SDK required: Any HTTP client works
Developer FAQ
Is the EmailCloud API free to use?
Yes. All 24 tools are free to try — your first check requires no signup at all. After that, we ask for a simple email login to prevent abuse and keep the service running for everyone. Register at POST /api/register with your email address to get an API key for continued and programmatic access.
What is MCP and how does it work with EmailCloud?
MCP (Model Context Protocol) is an open standard created by Anthropic that lets AI assistants connect to external tools and data sources. EmailCloud publishes an MCP server manifest at api.emailcloud.com/.well-known/mcp.json that describes all 24 tools with their inputs and outputs. AI assistants that support MCP — including Claude, Cursor, Windsurf, Cline, and LangChain — can discover and call EmailCloud tools automatically, giving them the ability to check SPF records, analyze email headers, grade subject lines, and run deliverability tests in real time.
What are the rate limits?
The deliverability test endpoint (GET /api/generate) is limited to 10 requests per minute per IP address to prevent abuse. All 23 instant tools have no rate limit — they run lightweight DNS queries and text analysis that complete in milliseconds. For high-volume programmatic access, register for a free API key to get tracked usage and priority handling.
Do I need to handle CORS?
The API allows cross-origin requests from emailcloud.com, www.emailcloud.com, and localhost:4321 (Astro dev server). For server-side calls from your backend, AI agent, or automation platform, CORS does not apply — call the endpoints directly. If you need additional frontend origins allowed, contact us.
Can I use the API in my own application or product?
Yes. The API is designed for integration. Use it in your SaaS product, internal tools, CI/CD pipelines, monitoring dashboards, or AI agents. Attribution to EmailCloud is appreciated but not required. For high-volume commercial use cases, register for an API key so we can ensure service quality.
How do I connect EmailCloud to ChatGPT?
Create a custom GPT with Actions configured to call api.emailcloud.com endpoints. Define each tool as an action with the appropriate HTTP method, URL, and JSON schema for inputs. ChatGPT will then be able to call EmailCloud tools when users ask email-related questions. Alternatively, use the OpenAI Assistants API with function definitions pointing to our endpoints.
How do I connect EmailCloud to Claude or Cursor via MCP?
Add the EmailCloud MCP server URL (https://api.emailcloud.com/.well-known/mcp.json) to your MCP client configuration. In Claude Desktop, add it under Settings > MCP Servers. In Cursor, add it under Settings > MCP. In Cline or Continue, add it to your MCP server list in the extension settings. The AI will automatically discover all 24 tools and their schemas.
What data do you store from API calls?
For instant tools (DNS checks, content analysis, calculators): we log the request IP and timestamp for rate limiting. We do not store your input data or results. For deliverability tests: the test email and results are stored temporarily (1-hour TTL) so you can poll for results, then automatically deleted. We never share, sell, or analyze your data beyond providing the tool results.
Start Building With EmailCloud
24 email tools. Zero cost. Zero signup. Point your agent at our MCP manifest or call the REST API directly. Your first result is one HTTP request away.