# subscriber.dev

> Open source lifecycle email for developers and AI agents. An alternative to Customer.io, Loops and Brevo with no dashboard: workflows, broadcasts and subscribers are managed over MCP, a REST API, a CLI and a TUI. Email sends through the user's own provider: Resend, Postmark, Amazon SES and Cloudflare Email are built in, with bounces and spam complaints handled; any other provider connects over SMTP.

## Connect

- MCP server (streamable HTTP): https://mcp.subscriber.dev
  - Claude Code: `claude mcp add --transport http subscriber https://mcp.subscriber.dev`
  - The first connection opens a browser to sign in. Signing in creates the account.
- CLI: `npx @subscriber.dev/cli login` prints a code and opens the browser to approve it. Run `subscriber` with no arguments for the TUI.
- REST API: https://api.subscriber.dev, authenticated with an API key in the `x-api-key` header. Each key belongs to one environment; create one with MCP `create_api_key` or `subscriber keys create <name>`. Keys are limited by default (trigger workflows, create or update subscribers); pass access "full" for everything else. The key decides the environment, so paths don't include one (e.g. POST /workflows/trigger); GET /keys/me shows which environment a key belongs to.

## Typical setup

1. Sign in over MCP or with the CLI.
2. Connect an email provider: resend, postmark, ses, cloudflare or smtp (MCP `set_integration`, CLI `subscriber integrations set resend`).
3. Create a workflow: an ordered list of email or webhook steps, each with a delay. Email bodies are HTML with Liquid, e.g. {{ subscriber.firstName }}. Optional `triggers` start it from integration events (e.g. Stripe trial_started) and `exitConditions` stop a person's run on others (e.g. Stripe trial_converted).
4. Trigger it from the app after an event such as signup:

```
POST https://api.subscriber.dev/workflows/trigger
x-api-key: <key>
content-type: application/json

{ "key": "welcome", "subscriber": { "email": "jane@acme.com" }, "payload": { "plan": "pro" } }
```

Workflow routes such as PATCH /workflows/{workflowId} take the workflow's public ID (12 lowercase letters and digits), not its key.

## What it does

- Workflows: event-driven email sequences with delays, triggers and exit conditions.
- Broadcasts: one-off sends to all opted-in subscribers or a tag, with an audience preview, sending spread over hours, and pause, resume and cancel.
- Subscribers: create, update, tag, bulk upsert (500 per request) and preferences.
- Integrations: Stripe events (trial_started, trial_ending, trial_converted, trial_payment_failed, trial_expired, subscription_started, subscription_canceled, payment_failed) as triggers and exit conditions.
- Deliverability: Every email gets one-click unsubscribe headers, which Gmail and Yahoo require of bulk senders, plus an unsubscribe link. Unsubscribed people are never sent to, hard bounces unsubscribe automatically, and every preference change is kept. Mail goes out through your own provider and domain, so SPF, DKIM and your reputation stay yours.
- Run history: every run and step, with the reason a step was skipped or cancelled.

## Pricing

Priced by opted-in subscribers. The free plan includes 10,000 sends a month (each email or webhook step run, including broadcasts); paid plans don't limit sends. Emails go out through the user's own provider, which bills for sending. Annual billing is 2 months free.

- free: 1,000 subscribers, 10,000 sends a month, $0
- starter: 5,000 subscribers, $19/month
- growth: 10,000 subscribers, $39/month
- scale: 25,000 subscribers, $79/month
- pro: 50,000 subscribers, $159/month
- business: 100,000 subscribers, $279/month
- custom: over 100,000, contact hello@subscriber.dev

Yes. It's open source under AGPL-3.0 and runs with Docker Compose. Self-hosting is free and unlimited. A $999/yr self-hosted Business license removes our branding and includes priority support, and Enterprise licenses cover AGPL exemptions.

## Email providers

The user pays their provider directly; subscriber.dev adds no markup. Prices checked October 2026.

- Amazon SES (US, EU, Asia, built in): $0.10 per 1k
- Scaleway (EU, SMTP): €0.25 per 1k
- Cloudflare Email (global, built in): $0.35 per 1k after 3k
- Resend (US, EU, more, built in): $20 for 50k
- SendGrid (US, EU, SMTP): $19.95 for 50k
- Mailgun (US, EU, SMTP): $15 for 10k, $35 for 50k
- Postmark (US, built in): $15 for 10k, +$1.80 per 1k

## Moving from another tool

Import subscribers through the bulk API or subscriber subscribers bulk, 500 at a time, or hand your agent an export and let it do the import. Describe your existing sequences and it can rebuild them as workflows.

## FAQ

### is there a web interface?

Not a dashboard. Everything works through the API, the CLI and TUI, or your AI agent over MCP.

### can I edit emails without code?

Yes. Ask your agent to rewrite it, or open the email in the web editor to tweak the copy and preview it before it sends. It's the only place you'll leave the terminal, and only if you want to.

### which AI agents does it work with?

Any MCP client: Claude, Claude Code, Cursor, ChatGPT, Codex and others. Add the server, sign in once in the browser, and your agent can create workflows, manage subscribers and send broadcasts.

### which email providers can I use?

Resend, Postmark, Amazon SES and Cloudflare Email are built in, with bounces and spam complaints handled automatically. Anything else with SMTP works too, such as SendGrid or Mailgun. You pay your provider directly, usually a few dollars a month.

### how do you handle deliverability?

Every email gets one-click unsubscribe headers, which Gmail and Yahoo require of bulk senders, plus an unsubscribe link. Unsubscribed people are never sent to, hard bounces unsubscribe automatically, and every preference change is kept. Mail goes out through your own provider and domain, so SPF, DKIM and your reputation stay yours.

### can I move from Loops or Customer.io?

Yes. Import subscribers through the bulk API or subscriber subscribers bulk, 500 at a time, or hand your agent an export and let it do the import. Describe your existing sequences and it can rebuild them as workflows.

### can I get my data out?

Any time. Everything is available through the API and CLI, and because it's open source you can self-host and take the whole database with you.

### can I self-host it?

Yes. It's open source under AGPL-3.0 and runs with Docker Compose. Self-hosting is free and unlimited. A $999/yr self-hosted Business license removes our branding and includes priority support, and Enterprise licenses cover AGPL exemptions.

### why did you build subscriber.dev?

We needed lifecycle email for Kan, and the options meant paying per contact and being locked into one email provider (usually SES at a large markup). We wanted our agent to set up and run it, sending through our own provider, and like Kan, we wanted it open source. Nothing did all three, so we built it.

### who's behind it?

Open Engineering, the team behind Kan, the open source Trello alternative. Kan's lifecycle and changelog emails, over 50,000 a month, all run on subscriber.dev.

## Email providers and costs (https://subscriber.dev/providers)

- Amazon SES: US, EU, Asia, built in, $0.10 per 1k. Pricing: https://aws.amazon.com/ses/pricing/
- Scaleway: EU, SMTP, €0.25 per 1k. Pricing: https://www.scaleway.com/en/pricing/managed-services/
- Cloudflare Email: global, built in, $0.35 per 1k after 3k. Pricing: https://developers.cloudflare.com/email-service/platform/pricing/
- Resend: US, EU, more, built in, $20 for 50k. Pricing: https://resend.com/pricing
- SendGrid: US, EU, SMTP, $19.95 for 50k. Pricing: https://www.twilio.com/en-us/products/email-api/pricing
- Mailgun: US, EU, SMTP, $15 for 10k, $35 for 50k. Pricing: https://www.mailgun.com/pricing/
- Postmark: US, built in, $15 for 10k, +$1.80 per 1k. Pricing: https://postmarkapp.com/pricing

What a month costs: 10,000 subscribers, each emailed 4 times a month (40,000 emails), on the growth plan at $39/month.

- Amazon SES: $4 sending + $39 = $43/month
- Scaleway: $12 sending + $39 = $51/month
- Cloudflare Email: $18 sending + $39 = $57/month
- Resend: $20 sending + $39 = $59/month
- SendGrid: $20 sending + $39 = $59/month
- Mailgun: $35 sending + $39 = $74/month
- Postmark: $69 sending + $39 = $108/month

## subscriber.dev vs Customer.io (https://subscriber.dev/vs/customer-io)

Customer.io is a full marketing platform with a visual journey builder and every channel. subscriber.dev does lifecycle email from your agent and terminal, for a fraction of the price.

- priced by: subscriber.dev opted-in subscribers; Customer.io profiles (people + objects)
- 5,000: subscriber.dev $19/mo; Customer.io $100/mo
- 10,000: subscriber.dev $39/mo; Customer.io $145/mo
- 25,000: subscriber.dev $79/mo; Customer.io $280/mo
- sends: subscriber.dev no limit on paid plans; Customer.io 1M emails/mo, then add-on
- free: subscriber.dev 1,000 subscribers; Customer.io trial
- AI agents: subscriber.dev MCP server; Customer.io MCP server, built-in agent
- sending: subscriber.dev your own provider; Customer.io theirs, or custom SMTP
- channels: subscriber.dev email, webhooks; Customer.io email, SMS, push, in-app
- open source: subscriber.dev AGPL-3.0, self-hostable; Customer.io no

Customer.io details from https://customer.io/pricing, checked October 2026.

Where subscriber.dev is different:
- a fifth of the price: Customer.io starts at $100 a month for 5,000 profiles. The same list is $19 here, with no limit on sends.
- only people who can receive email count: Customer.io bills every profile, including objects. We count opted-in subscribers, nothing else.
- built for agents and terminals: Everything works over MCP, the API, a CLI and a TUI, so there's no dashboard to learn.
- open source: AGPL-3.0 and self-hostable with Docker Compose, so you're never locked in.

When Customer.io is the better fit:
- You need SMS, push or in-app messages alongside email.
- A marketing team wants a visual journey builder and drag-and-drop editor.
- You want Customer.io's data pipelines to route events to other tools.

Switching: Import your people through the bulk API or the CLI, 500 at a time, or hand your agent a Customer.io export. Describe your campaigns and it can rebuild them as workflows, with Stripe events as triggers and exit conditions.

## subscriber.dev vs Loops (https://subscriber.dev/vs/loops)

Loops is a polished email platform for SaaS, sending on its own infrastructure. subscriber.dev sends through your provider, is open source, and costs less than half as much.

- priced by: subscriber.dev opted-in subscribers; Loops subscribed contacts
- free: subscriber.dev 1,000 subscribers; Loops 1,000 contacts
- free sends: subscriber.dev 10,000 a month; Loops 4,000 per 30 days
- 5,000: subscriber.dev $19/mo; Loops $49/mo
- 10,000: subscriber.dev $39/mo; Loops $99/mo
- 25,000: subscriber.dev $79/mo; Loops $199/mo
- sends: subscriber.dev no limit on paid plans; Loops unlimited on paid plans
- AI agents: subscriber.dev MCP server; Loops MCP server
- terminal: subscriber.dev CLI and TUI; Loops CLI
- sending: subscriber.dev your own provider; Loops Loops' infrastructure
- open source: subscriber.dev AGPL-3.0, self-hostable; Loops no

Loops details from https://loops.so/pricing, checked October 2026.

Where subscriber.dev is different:
- less than half the price: $39 a month for 10,000 subscribers against $99, and the gap holds at every tier.
- your provider, your reputation: Send through Resend, Postmark, Amazon SES, Cloudflare or any SMTP server. Your domain's reputation is yours, and you pay them directly.
- open source: AGPL-3.0 and self-hostable with Docker Compose, so you're never locked in.
- a TUI as well as a CLI: Watch runs, send broadcasts and manage workflows from a full terminal UI.

When Loops is the better fit:
- You'd rather not set up an email provider at all.
- You want to design emails in a visual editor with ready-made templates.
- You want transactional email, like receipts and password resets, through a dedicated API in the same tool.

Switching: Import your contacts through the bulk API or the CLI, 500 at a time, or hand your agent a Loops export. Describe your loops and it can rebuild them as workflows, with Stripe events as triggers and exit conditions.

## subscriber.dev vs Brevo (https://subscriber.dev/vs/brevo)

Brevo is an all-in-one marketing suite priced by how much you send. subscriber.dev is lifecycle email for developers and agents, priced by subscribers with no limit on sends.

- priced by: subscriber.dev opted-in subscribers; Brevo emails sent a month
- contacts: subscriber.dev your plan's subscribers; Brevo unlimited
- free: subscriber.dev 1,000 subscribers; Brevo 300 emails a day
- 5,000 × 4 emails: subscriber.dev $19/mo; Brevo $65/mo
- 25,000 × 4 emails: subscriber.dev $79/mo; Brevo $129/mo
- automation: subscriber.dev every plan; Brevo Standard plan and up
- sending: subscriber.dev your own provider; Brevo Brevo's infrastructure
- channels: subscriber.dev email, webhooks; Brevo email, SMS, WhatsApp, chat
- open source: subscriber.dev AGPL-3.0, self-hostable; Brevo no

Brevo details from https://www.brevo.com/pricing/, checked October 2026. Brevo rows assume four emails a month to each subscriber, on Brevo Standard, the first plan with automation.

Where subscriber.dev is different:
- sending more doesn't cost more: Brevo's price climbs with every email. Ours depends only on how many people you email, so a busier onboarding sequence costs nothing extra on a paid plan.
- automation on every plan: Workflows, triggers and exit conditions are on the free plan. Brevo needs Standard for automation.
- built for agents and terminals: Everything works over MCP, the API, a CLI and a TUI, so there's no dashboard to learn.
- open source: AGPL-3.0 and self-hostable with Docker Compose, so you're never locked in.

When Brevo is the better fit:
- You have a big list you email rarely, where unlimited contacts win.
- You want SMS, WhatsApp, live chat and a CRM in the same tool.
- A marketing team wants a drag-and-drop editor and landing pages.

Switching: Import your contacts through the bulk API or the CLI, 500 at a time, or hand your agent a Brevo export. Describe your automations and it can rebuild them as workflows, with Stripe events as triggers and exit conditions.

## Pages

- [Home](https://subscriber.dev/): what subscriber.dev does, with examples over MCP, the API, the CLI and the TUI, plus pricing and FAQ.
- [Email providers and costs](https://subscriber.dev/providers): supported providers, their prices and regions, and what a typical month costs.
- [subscriber.dev vs Customer.io](https://subscriber.dev/vs/customer-io): Customer.io is a full marketing platform with a visual journey builder and every channel. subscriber.dev does lifecycle email from your agent and terminal, for a fraction of the price.
- [subscriber.dev vs Loops](https://subscriber.dev/vs/loops): Loops is a polished email platform for SaaS, sending on its own infrastructure. subscriber.dev sends through your provider, is open source, and costs less than half as much.
- [subscriber.dev vs Brevo](https://subscriber.dev/vs/brevo): Brevo is an all-in-one marketing suite priced by how much you send. subscriber.dev is lifecycle email for developers and agents, priced by subscribers with no limit on sends.
- [Docs](https://docs.subscriber.dev): guides and API reference.
- [Source](https://github.com/kanbn/subscriber.dev): AGPL-3.0.
- [Full site as text](https://subscriber.dev/llms-full.txt): every page above in one file.

## Optional

- [Terms of service](https://subscriber.dev/terms)
- [Privacy policy](https://subscriber.dev/privacy)
- Contact: hello@subscriber.dev