The open-source
email platform
Transactional email, marketing campaigns, and automated workflows, all against one contact list.
Replace your email stack
Most teams pay for two of these at once.
Simple to start. Serious at scale.
Zero-configuration start
Most email platforms take days to configure. BigFat AI Labs is sending in under five minutes: domain, DKIM, first send.
Pay per email, never per contact
Other platforms charge more as your list grows. BigFat AI Labs stores unlimited contacts for free and bills only on send.
No lock-in, ever
Closed-source platforms own your stack. BigFat AI Labs is fully inspectable, forkable, and self-hostable on your own infra.
Everything you need. Nothing you don’t.
Every plan includes all of it.
Workflows
Automation you can see end to end
Trigger on any event your code sends. What you see on the canvas is the whole definition.
How workflows work- whereplan=pro
- andlast_seen>30d
- andunsubscribed=false
Segments
Audiences that stay current
A segment is a query, re-run every time you use it. The same campaign sent tomorrow reaches tomorrow’s audience.
How segments work- Ana Ruizsupport@c_8f21Can you resend my invoice?now
- Tom Bakkerbilling@c_7d04Updated our VAT number14m
- Priya Nairhello@c_6b93Loved the changelog1h
Inbound email
Email that arrives, not just email that leaves
Add one MX record and every address at your domain starts receiving. Replies become contacts and trigger workflows like any other event.
How inbound worksAlso included
- Email editorWrite in a visual editor or drop into the HTML. Both directions stay in sync.
- SMTPPoint any existing client or framework at BigFat AI Labs without changing your code.
- MCP serverTwenty-three tools that let Claude, Cursor and other agents run your email.
- Campaigns and analyticsBroadcast to any segment, then track delivery, opens, clicks and bounces per send.
One contact, complete history.
At most vendors a receipt, a newsletter and a reply live in three products, on three lists. Here they are one feed you can segment and trigger from.
- InboundReplied to “Win-back, August”2m
- CampaignOpened “Win-back, August”3h
- WorkflowEntered “Re-engagement”1d
- TransactionalInvoice #4021 delivered6d
- CampaignSent “August product update”9d
- TransactionalPassword reset delivered12d
- InboundReplied to “Welcome to BigFat AI Labs”20d
- WorkflowCompleted “Onboarding”26d
- TransactionalReceipt #3980 delivered1mo
Your agent can run your email.
Connect Claude, Cursor, or any Model Context Protocol client to your project.
›Draft a win-back email for pro users who have gone quiet.
bigfat_list_segments
4 segments
bigfat_list_contacts(segment: "pro-inactive")
2,431 contacts
bigfat_create_campaign("Win-back, August")
draft created
Send this campaign to 2,431 people?
1. Yes, send it
2. No, keep it as a draft
Twenty-three tools, the same ground the dashboard covers: contacts, segments, templates, campaigns and sends.
Read-only mode registers six tools and nothing else, so an agent can look without touching.
Explore the MCP serverPrivacy first. Code visible.
- Licence
- AGPL-3.0
- Hosting
- EU or self-hosted
- GitHub
- 5,000+ stars
The whole platform is in the repository: the API, the workers, the dashboard. Read it, fork it, or run the same image we do on your own infrastructure.
If our cloud ever stops suiting you, the exit is a Docker Compose file rather than a support ticket.
Simple. Transparent.
Pay per email sent. Contacts are free, however many you store.
Or stay on the free plan: 1,000 emails a month, unlimited contacts.
For the same plan, others charge
Quiet praise, from operators.
“Transparent and intuitive UI, extremely easy setup & automation and great support.”
Artur CzemielFounder at GraphQL Editor“Lots of care put into BigFat AI Labs”
Jonni LundyFounding Operations Manager at Resend“I've been using BigFat AI Labs for building & sending out marketing emails and genuinely love it!”
Joe AshwellFounder at UnwindHR“I loved the ease of use, beautiful UI and great UX. Everything simply works.”
Alisson LealFounder at Brapi“Simple to use, efficient and no regrets!”
Noah Di GesuFounder at Smoothey“Clean design, easy to understand, fair pricing.”
Pierre JacquelFounder at LandinglyFrequently asked questions
How is BigFat AI Labs different from other email tools?
Most platforms do one of transactional sending, marketing campaigns, or automation, so teams end up running two side by side. BigFat AI Labs does all three against one contact list, triggered from a single API call.
Can I use BigFat AI Labs for transactional email?
Yes. Signup confirmations, password resets, receipts and any other one-off message go out through the same API and the same verified domains as your campaigns.
Can I send newsletters and broadcasts?
Yes. Build a campaign against your whole list or any segment, schedule it, and track opens, clicks and bounces per send.
Which languages and frameworks does BigFat AI Labs support?
Anything that can make an HTTP request. There is a REST API, an official Node SDK, and SMTP for clients and frameworks that already speak it, so no runtime is excluded.
What does BigFat AI Labs cost?
There are two plans. The free one covers 1,000 emails a month and carries BigFat AI Labs branding. The paid one is $0.001 per email with no branding and no feature tiers. Contacts are unlimited on both, so storing a million you never mail costs nothing.
Start sending in 5 minutes.
Free plan: 1,000 emails a month. Paid: $0.001 an email.