# SMTPfast

> SMTPfast is a transactional email API for developers, built on AWS SES: domain verification, email sending API, SMTP bridge, broadcasts, contact forms, webhooks, suppression management, and real-time delivery analytics.

- API base: https://smtpfa.st/api/v1
- OpenAPI spec: https://smtpfa.st/api/v1/openapi.json
- Hosted MCP server: https://smtpfa.st/api/mcp
- Blog RSS: https://smtpfa.st/feed.xml
- Full text for AI systems: https://smtpfa.st/llms-full.txt

## Docs

- [Documentation](https://smtpfa.st/docs): Quickstart and API reference
- [Authentication](https://smtpfa.st/docs/authentication): Bearer token authentication with API keys and the scopes each key can hold.
- [Emails](https://smtpfa.st/docs/emails): Send transactional email, single or in batches, schedule sends, and read delivery status and events.
- [Domains](https://smtpfa.st/docs/domains): Add sending domains, publish the DNS records, verify ownership, and claim a domain another account never verified.
- [API Keys](https://smtpfa.st/docs/api-keys): Create, list, and revoke API keys programmatically, with per-key scopes.
- [Webhooks](https://smtpfa.st/docs/webhooks): Real-time notifications for email, domain, and contact events, with signatures, retries, and a delivery log.
- [Contacts](https://smtpfa.st/docs/contacts): Subscribers with subscription state, custom properties, manual segments, and a flag for throwaway-mailbox domains.
- [Signup Forms](https://smtpfa.st/docs/forms): Embeddable signup forms that feed submissions into the Contacts API.
- [Rate Limits](https://smtpfa.st/docs/rate-limits): Request limits per plan and how to handle throttling responses.
- [Data Retention](https://smtpfa.st/docs/data-retention): The 30-day window on rendered email bodies, and what stays with your account.
- [Resend Compatibility](https://smtpfa.st/docs/resend): API compatibility with Resend: switch by changing the base URL and the API key.
- [Broadcasts](https://smtpfa.st/docs/broadcasts): One-to-many campaigns to subscribed contacts, with scheduling, test sends, and per-broadcast metrics.
- [Templates](https://smtpfa.st/docs/templates): Reusable emails with variables, a draft and a published version, sent by id or alias; compatible with Resend's Templates API.
- [Live Tail](https://smtpfa.st/docs/live-tail): Stream every send, delivery, bounce, open, click, and complaint as it happens.
- [Logs](https://smtpfa.st/docs/logs): Query the event log by type, time, recipient, and email, and page through it for auditing or backfills.
- [MCP Server](https://smtpfa.st/docs/mcp): Hosted Model Context Protocol server for AI assistants: connection setup with an API key and the tools it exposes.
- [Claude Skill](https://smtpfa.st/docs/skill): The SMTPfast Agent Skill for Claude: what it does and how to install it.
- [Teams](https://smtpfa.st/docs/teams): Shared workspaces with roles that control who can send, manage, and configure.
- [Inbound](https://smtpfa.st/docs/inbound): Receive mail on a sending domain; messages are parsed, stored for 30 days, and delivered by webhook or API.
- [Inboxes](https://smtpfa.st/docs/inboxes): Turn an address on your own domain into a mailbox with threads, folders, labels and drafts; Resend-compatible, with drafts as the review step for agents.

## Pages

- [Home](https://smtpfa.st/): Email API for developers
- [Pricing](https://smtpfa.st/pricing): Plans and pay-as-you-go pricing
- [Status](https://smtpfa.st/status): Live system status
- [Tools](https://smtpfa.st/tools): Free email infrastructure tools
- [Spf Checker](https://smtpfa.st/tools/spf-checker)
- [Dkim Checker](https://smtpfa.st/tools/dkim-checker)
- [Dmarc Checker](https://smtpfa.st/tools/dmarc-checker)
- [Mx Checker](https://smtpfa.st/tools/mx-checker)
- [Email Header Analyzer](https://smtpfa.st/tools/email-header-analyzer)
- [Markdown Email Preview](https://smtpfa.st/tools/markdown-email-preview)
- [Spam Checker](https://smtpfa.st/tools/spam-checker)
- [Email Validator](https://smtpfa.st/tools/email-validator)
- [Bimi Checker](https://smtpfa.st/tools/bimi-checker)
- [Subject Line Tester](https://smtpfa.st/tools/subject-line-tester)
- [Image Metadata Cleaner](https://smtpfa.st/tools/image-metadata-cleaner)
- [Email Compatibility Checker](https://smtpfa.st/tools/email-compatibility-checker)
- [Mail Tester](https://smtpfa.st/tools/mail-tester)

## Comparisons

- [Smtpfast Vs Resend](https://smtpfa.st/compare/smtpfast-vs-resend)
- [Smtpfast Vs Sendgrid](https://smtpfa.st/compare/smtpfast-vs-sendgrid)
- [Smtpfast Vs Mailgun](https://smtpfa.st/compare/smtpfast-vs-mailgun)
- [Smtpfast Vs Postmark](https://smtpfa.st/compare/smtpfast-vs-postmark)
- [Smtpfast Vs Amazon Ses](https://smtpfa.st/compare/smtpfast-vs-amazon-ses)
- [Smtpfast Vs Plunk](https://smtpfa.st/compare/smtpfast-vs-plunk)
- [Smtpfast Vs Mailchimp](https://smtpfa.st/compare/smtpfast-vs-mailchimp)
- [Smtpfast Vs Customer Io](https://smtpfa.st/compare/smtpfast-vs-customer-io)
- [Smtpfast Vs Brevo](https://smtpfa.st/compare/smtpfast-vs-brevo)
- [Smtpfast Vs Mailjet](https://smtpfa.st/compare/smtpfast-vs-mailjet)
- [Smtpfast Vs Loops](https://smtpfa.st/compare/smtpfast-vs-loops)
- [Smtpfast Vs Buttondown](https://smtpfa.st/compare/smtpfast-vs-buttondown)
- [Smtpfast Vs Convertkit](https://smtpfa.st/compare/smtpfast-vs-convertkit)
- [Smtpfast Vs Smtp2go](https://smtpfa.st/compare/smtpfast-vs-smtp2go)

## Blog

Append .md to any post URL for the raw markdown version.

- [The Best Free SMTP Services for Developers in 2026](https://smtpfa.st/blog/best-free-smtp-services-2026): Ten free SMTP services compared for apps, CMSs and devices: free-tier limits, daily caps, ports and TLS. Every number checked on the provider's own pages.
- [Best Transactional Email Services for SaaS in 2026](https://smtpfa.st/blog/best-transactional-email-services-for-saas-2026): SMTPfast, Mailtrap, Postmark, Twilio SendGrid and Amazon SES compared for SaaS products: free tiers, real prices, inbound email, and the tradeoffs each one makes.
- [Everything in the dashboard is now an API, and there is a CLI](https://smtpfa.st/blog/headless-api-and-cli): Every action in the SMTPfast dashboard now has an API endpoint, the hosted MCP server covers almost all of it, and a new command-line tool turns each endpoint into a command. Tests keep all four in step.
- [Hosted email templates: write once, send by id](https://smtpfa.st/blog/hosted-email-templates): SMTPfast now stores your email templates. Write one with variables, preview it on desktop, mobile and dark mode, publish it, and send it by id or alias. The API matches Resend's Templates API.
- [Inboxes: threads, labels and agent drafts on your own domain](https://smtpfa.st/blog/inboxes-on-your-own-domain): Turn support@yourdomain.com into a real inbox inside SMTPfast. Received mail and your replies group into threads, and AI agents can write drafts that a person reviews and sends. The API matches Resend's Inboxes API.
- [DigitalOcean Blocks SMTP on Droplets: How to Send Email From Your App Anyway](https://smtpfa.st/blog/digitalocean-smtp-blocked): DigitalOcean blocks outbound SMTP ports 25, 465 and 587 on Droplets and advises against running your own mail server. Here is how to tell if the block is what broke your emails, and two ways around it: an HTTPS API on port 443, or SMTP on port 2525.
- [One approval instead of five DNS records: Domain Connect on SMTPfast](https://smtpfa.st/blog/domain-connect-one-click-dns): If your domain is on Cloudflare, SMTPfast can publish its sending records, and separately the inbound MX, through Domain Connect. You review each set on Cloudflare's screen, approve, and the records are written for you. Here is how it works, what gets written, and what to do when your DNS lives elsewhere.
- [Logs API and webhook deliveries: answer 'did it send?' without opening the dashboard](https://smtpfa.st/blog/logs-api-and-webhook-deliveries): Two additions for the debugging side of email: the event log behind the Logs page is now an API, and every webhook has a delivery log with attempts, responses, automatic retries and a retry button.
- [Inbound email: receive mail on your domain, read it through the API](https://smtpfa.st/blog/inbound-email): SMTPfast now receives email on your verified domains. Enable it per domain, publish one MX record, and mail for any address on that domain reaches your Inbound page, the receiving API and an email.received webhook.
- [How SMTPfast Uses AI to Keep Bad Actors Off the Platform](https://smtpfa.st/blog/ai-signup-screening): Applications for sending access are now researched and risk-scored by an AI system built on DigitalOcean's AI platform, so humans make the final call with the evidence already gathered. Here is how it works and why it matters for everyone sending through the platform.
- [Feedletter: Turn an RSS Feed or Markdown Folder into a Newsletter](https://smtpfa.st/blog/feedletter-newsletter-from-rss-or-markdown): A free, open-source CLI and browser studio that reads your RSS feed or Markdown content, lets you curate and preview the issue, and sends it with SMTPfast. Per-recipient unsubscribe, history so nothing goes out twice, and a GitHub Action for hands-off sends.
- [Manage SMTPfast as Code with the Terraform Provider](https://smtpfa.st/blog/terraform-provider): Register sending domains, publish DKIM/SPF/DMARC records, mint API keys, and wire up webhooks from Terraform. Reproducible email infrastructure, reviewed in a pull request instead of clicked together in a dashboard.
- [The Boring Stack Behind SMTPfast (And Why Boring Is Reliable)](https://smtpfa.st/blog/boring-reliable-stack): SMTPfast runs on a deliberately small stack: a Next.js app, Postgres, a Redis queue, a worker, and Amazon SES. Here is the whole architecture, and why fewer moving parts is exactly what makes your email arrive.
- [Teams in SMTPfast: shared workspaces, roles, and invites](https://smtpfa.st/blog/team-collaboration): Bring your teammates and clients into one workspace. Shared domains, contacts, and API keys, with roles that keep billing and member management where they belong.
- [Prepaid Email Credits for SMTPfast](https://smtpfa.st/blog/prepaid-email-credits): Buy optional overflow email credits for traffic spikes without changing your monthly plan. Your plan allowance is used first, then credits cover extra accepted emails.
- [Auto-welcome email on every signup form](https://smtpfa.st/blog/auto-welcome-email-on-form-signup): Every SMTPfast signup form can now send a welcome email the moment a subscriber confirms. Two text fields and a save. Welcome emails open at 50-70% on a typical SaaS list, against 15-32% for broadcasts.
- [Broadcast Campaigns in SMTPfast](https://smtpfa.st/blog/broadcast-campaigns): Broadcasts let you send product updates and newsletters to subscribed contacts with drafts, tests, scheduling, suppression checks, and delivery metrics.
- [Best Email API in 2026: An Engineer's Honest Comparison](https://smtpfa.st/blog/best-email-api-2026): Nine transactional email APIs ranked by what matters: developer experience, pricing, deliverability, and where each one breaks. Code samples for every one.
- [Live Tail: real-time email event logs in your dashboard](https://smtpfa.st/blog/live-tail-real-time-email-logs): Watch every send, delivery, bounce, open, and click stream into your dashboard in real time. tail -f for email.
- [Add a signup form to your website in 5 minutes](https://smtpfa.st/blog/embeddable-signup-forms): Drop a form on your site, collect contacts straight into SMTPfast, with double opt-in and webhook events out of the box.
- [API Key Security: Best Practices for Email APIs](https://smtpfa.st/blog/api-key-security): A leaked API key can send thousands of emails on your behalf in minutes. Here is how to keep your keys safe.
- [DKIM, SPF, and DMARC Explained: The Complete Guide](https://smtpfa.st/blog/domain-authentication-guide): Three DNS records stand between your emails and the spam folder. Here is what each one does and exactly how to set them up.
- [How to Build and Protect Your Email Sender Reputation](https://smtpfa.st/blog/email-reputation-guide): Your sender reputation determines whether emails reach the inbox or land in spam. Here is how to build it from scratch and keep it healthy.
- [Mailgun vs SMTPfast: Developer Email API Comparison](https://smtpfa.st/blog/mailgun-vs-smtpfast): Mailgun has been a developer favorite for years. SMTPfast is the new challenger. Here is how they stack up on DX, pricing, and features.
- [How to Migrate from SendGrid to SMTPfast](https://smtpfa.st/blog/migrate-from-sendgrid): A step-by-step guide to moving your transactional email from SendGrid to SMTPfast. Includes code before and after for every language.
- [Send Emails from Node.js in 5 Minutes with SMTPfast](https://smtpfa.st/blog/node-send-email-tutorial): No SDK, no dependencies. Just fetch() and a few lines of code to send transactional emails from your Node.js app.
- [Postmark vs SMTPfast: Transactional Email Compared](https://smtpfa.st/blog/postmark-vs-smtpfast): Postmark built its reputation on delivery speed. SMTPfast built its on developer simplicity. Here is how they compare.
- [Send Transactional Emails from Python with SMTPfast](https://smtpfa.st/blog/python-send-email-tutorial): Use the requests library to send emails from any Python app. Includes FastAPI and Django integration patterns.
- [SendGrid vs SMTPfast: Which Email API Should You Choose?](https://smtpfa.st/blog/sendgrid-vs-smtpfast): An honest head-to-head comparison of SendGrid and SMTPfast. Where each wins, where each falls short, and who should pick what.
- [Email Webhook Best Practices: Handle Bounces, Complaints, and Deliveries](https://smtpfa.st/blog/webhook-best-practices): Webhooks are how your app stays in sync with email delivery. Here is how to set them up correctly and handle every event type.
- [How to Switch from Resend to SMTPfast in 5 Minutes](https://smtpfa.st/blog/switching-from-resend-to-smtpfast): SMTPfast is API-compatible with Resend. Switch by changing two lines of code: your base URL and API key.
- [Getting Started with SMTPfast](https://smtpfa.st/blog/getting-started): Sign up, verify a domain, mint an API key, and send your first email through SMTPfast in about ten minutes. Curl, Node, and Python examples included.
- [Email Deliverability: Why Your Emails Land in Spam](https://smtpfa.st/blog/email-deliverability-guide): The actual reasons mail lands in spam: weak DKIM/SPF/DMARC, dirty lists, complaint rate, content tells, and IP warmup. With concrete fixes for each.
- [Transactional vs Marketing Emails: What is the Difference?](https://smtpfa.st/blog/transactional-vs-marketing-emails): Understanding the difference between transactional and marketing emails, and why it matters for deliverability and compliance.
- [Resend vs SendGrid vs SMTPfast: Which Email API to Use](https://smtpfa.st/blog/resend-vs-sendgrid-vs-smtpfast): An honest comparison of three email API providers. Pricing, features, developer experience, and who each one is best for.
- [10 Reasons Your Emails Land in Spam (And How to Fix Each One)](https://smtpfa.st/blog/why-emails-go-to-spam): A developer's checklist of the ten signals every spam filter scores you on, with concrete fixes and the specific DNS records, headers, and metrics that matter.
- [Email API Best Practices for Production Apps](https://smtpfa.st/blog/email-api-best-practices): Lessons from sending millions of transactional emails. Error handling, retry logic, templates, and monitoring.
- [Building Email Templates with React (No Framework Required)](https://smtpfa.st/blog/react-email-templates): Build readable, type-safe email templates with React Email. Covers setup, rendering, local preview, Tailwind, Outlook quirks, and plain text generation.
- [AWS SES Setup: From Zero to Production in 30 Minutes](https://smtpfa.st/blog/aws-ses-setup-guide): A step-by-step guide to setting up AWS SES for email sending. Domain verification, sending limits, and production access.