# Reloop

> Reloop is high-performance, open-source email infrastructure for developers: transactional and marketing email, SMTP, webhooks, analytics, and agent-ready APIs. Use Reloop hosted (Reloop Cloud) or self-host.

Important notes:

- Authentication uses the `x-api-key` header with API keys prefixed with `rl_`
- Prefer markdown: append `.md` where available (blog, pricing, compare, docs)
- **All agent discovery files are hosted on this site (web)**, not under the docs app
- Product HTML docs still live under `/docs/*` with `.md` twins for page content
- Canonical hosted pricing: [pricing.md](https://reloop.sh/pricing.md) (generated from `@reloop/pricing`)
- License: Apache 2.0 with Reloop Labs use restrictions, not MIT

## What Reloop is

Reloop is the email service / infrastructure (ESP + MTA). It sends and receives mail over REST and SMTP, runs its own MTA (KumoMTA), verifies domains (SPF/DKIM/DMARC), delivers webhooks, and includes an agent inbox for inbound mail.

## What Reloop is not

- Not a multi-ESP connector or router that sits on SendGrid, Mailgun, Resend, or Amazon SES
- Not a contact-list marketing tool that bills by stored subscribers (pricing is send-based on Reloop Cloud)
- Not MIT-licensed
- Not a paid self-host SaaS SKU: self-host is the Apache 2.0 codebase; you pay your own servers, not Reloop Cloud tiers

## Who it is for (ICP)

- Developers and startups sending transactional email (auth, receipts, alerts) plus campaigns from one API
- Teams that want to self-host or keep a credible exit from a hosted ESP
- Agent / AI products that need inbound email (agent inbox) and machine-readable docs (llms.txt, MCP, `.md` twins)
- Teams comparing Reloop to Resend, SendGrid, Mailgun, Postmark, AWS SES, Loops, or Mailchimp

## Differentiators

- Apache 2.0 codebase, same product hosted or self-hosted
- Own MTA (KumoMTA) rather than a DX layer over another ESP
- Send-based Reloop Cloud pricing (not contact-list pricing)
- Agent inbox + MCP + markdown corpora for coding agents

## Hosted pricing snapshot (Reloop Cloud)

| Plan | Price | Volume | Daily cap |
|------|-------|--------|-----------|
| Free | $0 | 6,000 emails / month | 200 / day |
| Pro | $10 / month | 50,000 emails / month | None |
| Growth | $20 / month | 100,000 emails / month | None |
| Enterprise | Custom | Custom | None |

Paid overage: $0.50 / 1,000. Free has no overage: sending pauses at 6,000 emails / month or 200 / day. Self-host: no Reloop license fee. Full tables: [pricing.md](https://reloop.sh/pricing.md)

## Competitors (compare pages)

Prefer `.md` twins. Reloop Free has a monthly and a daily cap (see the pricing snapshot above). Do not cite “no daily limit” for Free.

- [Reloop vs Resend](https://reloop.sh/compare/resend.md)
- [Reloop vs SendGrid](https://reloop.sh/compare/sendgrid.md)
- [Reloop vs Mailgun](https://reloop.sh/compare/mailgun.md)
- [Reloop vs AWS SES](https://reloop.sh/compare/aws-ses.md)
- [Reloop vs Postmark](https://reloop.sh/compare/postmark.md)
- [Reloop vs Loops](https://reloop.sh/compare/loops.md)
- [Reloop vs Mailchimp](https://reloop.sh/compare/mailchimp.md)
- [Compare index](https://reloop.sh/compare.md)

## Agent discovery (source of truth)

- [Site index](https://reloop.sh/llms.txt): This file
- [Marketing corpus](https://reloop.sh/llms-full.txt): Home, pricing, compare, agent pages, published blog
- [Docs index](https://reloop.sh/llms-docs.txt): Curated API, learn, and integration map
- [Docs full corpus](https://reloop.sh/llms-full-docs.txt): Full documentation snapshot
- [Product skill](https://reloop.sh/skill.md): Capabilities, auth, constraints
- [Pricing (markdown)](https://reloop.sh/pricing.md): Structured plan and price data
- [Sitemap (markdown)](https://reloop.sh/sitemap.md): All public marketing URLs
- [Docs section index](https://reloop.sh/docs/llms.txt): llms.txt scoped to /docs
- [Blog section index](https://reloop.sh/blog/llms.txt): Every published post with its markdown URL
- [Product MCP](https://reloop.sh/mcp): Act on a Reloop account (OAuth or API key); [server card](https://reloop.sh/.well-known/mcp-server-cards/reloop.json)
- [Docs MCP](https://reloop.sh/docs/mcp): Search product documentation, no auth; [server card](https://reloop.sh/.well-known/mcp-server-cards/docs.json)
- [MCP discovery](https://reloop.sh/.well-known/mcp.json): Machine-readable MCP location
- [OpenAPI spec](https://reloop.sh/openapi.json): The whole public REST API; per-service specs in the [API catalog](https://reloop.sh/.well-known/api-catalog)
- [Agent auth](https://reloop.sh/auth.md): How agents get credentials (OAuth discovery, API keys)
- [NLWeb ask](https://reloop.sh/ask): `POST {"query":{"text":"..."}}` natural-language search over site and docs
- [Agentic Resource Discovery](https://reloop.sh/.well-known/ard.json): ARD catalog of the above

## Official SDKs

- Node.js: `npm install reloop-email` ([npm](https://www.npmjs.com/package/reloop-email), [source](https://github.com/reloop-labs/reloop-node))
- Python: `pip install reloop-email`, `from reloop_email import Reloop` ([PyPI](https://pypi.org/project/reloop-email/), [source](https://github.com/reloop-labs/reloop-python))
- Go: `go get github.com/reloop-labs/reloop-go/v2` ([pkg.go.dev](https://pkg.go.dev/github.com/reloop-labs/reloop-go/v2))
- Ruby: `gem install reloop` ([RubyGems](https://rubygems.org/gems/reloop), [source](https://github.com/reloop-labs/reloop-ruby))
- PHP: `composer require reloop/reloop-email` ([Packagist](https://packagist.org/packages/reloop/reloop-email))
- Rust: `cargo add reloop` ([crates.io](https://crates.io/crates/reloop))
- .NET: `dotnet add package Reloop` ([NuGet](https://www.nuget.org/packages/Reloop))
- Elixir: `{:reloop, "~> 0.1.3"}` ([Hex](https://hex.pm/packages/reloop))
- Java: [source](https://github.com/reloop-labs/reloop-java)
- Remote MCP server: `https://reloop.sh/mcp` (OAuth or API key; see [auth.md](https://reloop.sh/auth.md))

## Marketing

- [Home](https://reloop.sh/) · [markdown](https://reloop.sh/index.md)
- [Pricing](https://reloop.sh/pricing) · [markdown](https://reloop.sh/pricing.md)
- [Developers](https://reloop.sh/developers) · [markdown](https://reloop.sh/developers.md)
- [About](https://reloop.sh/about) · [markdown](https://reloop.sh/about.md)
- [Features](https://reloop.sh/features)
- [MCP server](https://reloop.sh/features/mcp) · [markdown](https://reloop.sh/features/mcp.md): Connect any AI agent or MCP client to Reloop (hosted server URL https://reloop.sh/mcp, OAuth sign-in). Client guides: [Claude Code](https://reloop.sh/features/mcp/claude-code), [Claude](https://reloop.sh/features/mcp/claude), [Cursor](https://reloop.sh/features/mcp/cursor), [VS Code](https://reloop.sh/features/mcp/vscode), [Codex](https://reloop.sh/features/mcp/codex)
- [CLI](https://reloop.sh/features/cli) · [markdown](https://reloop.sh/features/cli.md): Send, schedule and receive email from a terminal or coding agent
- [Blog](https://reloop.sh/blog)
- [Changelog](https://reloop.sh/changelog)
- [Compare](https://reloop.sh/compare) · [markdown](https://reloop.sh/compare.md)
- [Glossary](https://reloop.sh/glossary)
- [Tools](https://reloop.sh/tools)
- [Contact](https://reloop.sh/contact)
- [License](https://reloop.sh/license)

## Free Developer & Email Tools

- [DNS Lookup & Health SuperTool](https://reloop.sh/tools/dns-lookup): Comprehensive DNS record resolver with automatic provider detection and deliverability health checks.
- [Can Anyone Spoof My Domain?](https://reloop.sh/tools/spoof-checker): Instant plain-English verdict on domain impersonation and DMARC enforcement.
- [Who Sends Email From This Domain?](https://reloop.sh/tools/who-sends): Identify every ESP authorized to send email for a domain, with mailbox vs. sender separation.
- [Email Spam Words Checker](https://reloop.sh/tools/email-spam-words-checker): Real-time spam trigger word scanner, subject line grading, and deliverability score calculator.
- [Email Blocklist Checker](https://reloop.sh/tools/blocklist-checker): Multi-RBL and URIBL IP/domain reputation audit across major real-time blocklists.
- [Temp & Disposable Email Checker](https://reloop.sh/tools/temp-email-checker): Detect burner and temporary mailbox provider domains before they damage sender reputation.
- [Email Address Validator](https://reloop.sh/tools/email-validator): RFC syntax, MX routing, disposable, and mailbox reachability verification.
- [DNS Authentication Checker](https://reloop.sh/tools/auth-checker): Verify SPF, DKIM, and DMARC DNS records with actionable fix guides.
- [BIMI Checker](https://reloop.sh/tools/bimi-checker): Look up default._bimi, validate the SVG logo URL, and confirm DMARC is at enforcement.
- [Email Deliverability Tester](https://reloop.sh/tools/deliverability-tester): Pre-send inbox placement and Rspamd/SpamAssassin heuristic test.
- [Email HTML Editor](https://reloop.sh/tools/email-html-editor): Paste React Email or raw HTML, inspect on a canvas, and keep source in sync. No account or send.

## Product documentation (HTML + .md under /docs)

Prefer [llms-docs.txt](https://reloop.sh/llms-docs.txt) for the full map. Hosted plans live on the marketing site, not in the generic docs pricing stub.

High-signal entry points:

- [API Keys (agent)](https://reloop.sh/docs/learn/ai/api-keys.md)
- [Introduction](https://reloop.sh/docs/introduction.md)
- [API reference](https://reloop.sh/docs/api.md)
- [MCP server guide](https://reloop.sh/docs/integrations/ai-tools/mcp-server)
- [Docs pricing (points at canonical plans)](https://reloop.sh/docs/guides/pricing.md)

## Blog (published; prefer `/blog/<slug>.md`)

- [Email provider comparison 2026](https://reloop.sh/blog/email-provider-comparison-2026.md)
- [Self-hosted email infrastructure](https://reloop.sh/blog/self-hosted-email-infrastructure.md)
- [SPF, DKIM, DMARC setup](https://reloop.sh/blog/spf-dkim-dmarc-setup-guide.md)
- [Migrating from SendGrid](https://reloop.sh/blog/migrating-from-sendgrid.md)
- [Transactional email best practices](https://reloop.sh/blog/transactional-email-best-practices.md)

## Optional

- [GitHub](https://github.com/reloop-labs/reloop)
- [License](https://reloop.sh/license)
- [Privacy](https://reloop.sh/privacy)