# Plunk

> Plunk is an open-source email platform for SaaS teams and developers that combines transactional sending, broadcast campaigns, and visual workflow automation on a single contact record, built on top of Amazon SES, priced at $0.001 per email with unlimited contacts and no monthly fee, and available to self-host under AGPL-3.0 via Docker Compose.

- Category: Marketing Automation (https://saastracker.org/categories/marketing-automation)
- Website: https://www.useplunk.com
- Starting price: $0 (free tier), then $0.001 per email
- Free plan: 1,000 emails a month with no credit card required and every feature included; the only limitation is Plunk branding on messages.
- Free trial: No separate trial; the free tier is permanent and functionally complete.
- Founded: 2022, HQ: Europe, Ownership: Independent and bootstrapped, with the product open sourced under AGPL-3.0
- Profile last reviewed: 2026-08-22
- Canonical profile: https://saastracker.org/products/plunk

## Overview

Plunk exists because the split between transactional and marketing email is an artefact of how vendors bill rather than anything a product actually wants. Your password reset goes through one tool, your onboarding sequence through another, your newsletter through a third, and the same person exists three times with three unsubscribe states. Plunk puts all three on one contact record with one activity history, one set of segments, and one sending identity, and charges a flat $0.001 per email with no monthly fee and no contact meter at all.

It is an indie project rather than a venture-backed platform. Dries Augustyns built it, launched it as a proprietary tool, and open-sourced the whole thing under AGPL-3.0 in August 2024. The GitHub repository has passed 5,000 stars, and the hosted service is run by one person with no outside funding. That is either the most attractive or the most disqualifying fact about Plunk depending on what you are buying it for, and both readings are defensible.

Architecturally it is event-driven in the lightweight sense. You track events from your application through the API, and workflows trigger from those events with delays, conditions, and sends. Segments recompute from contact data and behaviour. There is no separate product analytics layer, no warehouse connector, and no multi-channel orchestration; Plunk is email and only email. What it does have that most cheap email tools do not is a genuinely unified transactional path, so a receipt and a lifecycle email leave from the same authenticated domain with the same reputation.

The commercial model deserves attention because it is unusual. Every feature is on every plan: API access, custom domains, analytics, segmentation, workflows, campaigns, and inbound email are all included whether you pay nothing or a hundred dollars. The free tier is 1,000 emails a month with Plunk branding on messages, and the paid path removes the branding and charges purely by volume. Self-hosting is free of licence cost entirely, and you pay only your own infrastructure and your own SES bill.

## How it works

1. You create a contact for each user, either through the API or by importing, and attach whatever custom fields matter. Contacts are unlimited and never metered, which removes the single biggest cost anxiety in email marketing tooling.

2. Your application tracks events through the API at the points that matter: signed up, upgraded, invited a teammate, cancelled. Those events attach to the contact's activity history and become workflow triggers.

3. Workflows are drawn in a visual builder with triggers, delays, and conditional logic, sending email at each step. The same platform sends your transactional mail directly through the API, so a receipt and a day-three onboarding email leave from the same domain with the same reputation.

4. Delivery sits on Amazon SES underneath. On the hosted service Plunk manages that for you; when self-hosting you supply your own SES credentials, so your per-email cost drops to the SES rate and the only remaining expense is the server running Plunk itself.

## Best for

SaaS teams, indie hackers, and developer-led products that want transactional email, onboarding automations, and broadcasts on one contact record at usage-based pricing, and who either value open source on principle or want the option to self-host and stop paying per email entirely.

## Not the right fit for

- Marketing teams without engineering support; contacts and events arrive through the API, and while campaigns and workflows are usable in the interface, nothing works until somebody instruments the events.
- Multi-channel lifecycle programmes; Plunk is email only, with no SMS, no push, no in-app messaging, and no plans advertised to add them.
- Companies that need vendor assurances: there is no SOC 2 report, no enterprise support contract, no SLA, and the hosted service is run by one person with no outside funding.
- Design-led marketing teams who want a rich template gallery, brand kits, and visual polish; Plunk's editor is functional and developer-flavoured rather than a design tool.
- Businesses whose funnel is landing pages, forms, popups, and lead scoring; Plunk has none of that apparatus and expects your product to be the acquisition surface.

## Features

### Unified email

The structural idea: transactional and marketing on one contact and one reputation.

- **Transactional sending**: Receipts, password resets, and system notifications sent through the API, logged against the same contact record as everything else so support can see the whole history in one place.
- **Broadcast campaigns**: Newsletters and product updates with scheduling and performance tracking, sent from the same platform and the same authenticated domain as your transactional mail.
- **One contact, one history**: A single record holds custom fields, event history, campaign engagement, and transactional sends, which removes the reconciliation problem created by running two email tools.
- **Unlimited contacts at no charge**: Contacts are never metered on any plan. You pay only for emails sent, which inverts the pricing model of nearly every marketing email tool and removes the incentive to prune a list for billing reasons.
- **Inbound email**: Receive and process incoming mail with webhook notifications, so replies can route into your application rather than into a shared mailbox nobody reads.

### Automation

A visual workflow builder driven by events from your own application.

- **Visual workflow builder**: Multi-step sequences with triggers, delays, and conditional logic, built without code, and included on the free plan like everything else.
- **Event-triggered flows**: Workflows start from events you track through the API, so onboarding, activation, and churn-risk sequences fire off real product behaviour rather than list membership.
- **Conditional branching**: Branch on contact fields or prior behaviour so one workflow serves several user states rather than duplicating flows.
- **Delays and scheduling**: Wait steps measured in the units a lifecycle sequence needs, handled by Plunk rather than by a job queue in your application.
- **Real-time segmentation**: Segments computed from contact data and behaviour, updating as events arrive, usable for both campaign targeting and workflow conditions.

### Sending and deliverability

Amazon SES underneath, with your domain and your authentication.

- **Custom sending domains**: Branded sending with DKIM and SPF authentication, included on every plan rather than reserved for paid tiers.
- **Built on Amazon SES**: Delivery runs on SES, which means predictable infrastructure and, when self-hosting, direct SES rates rather than a vendor margin on every message.
- **Delivery analytics**: Opens, clicks, bounces, and conversion tracking across campaigns and workflows, with per-contact engagement history.
- **Branding removal**: Plunk branding appears on free-tier messages and is removed on the paid plan, which is the only functional difference between the two.

### Open source and self-hosting

The escape hatch, and the reason a cost-sensitive team should look here first.

- **AGPL-3.0 licensed**: The full source is public under AGPL-3.0 with more than 5,000 GitHub stars. You can read exactly what happens to your data and fork it if the project stops.
- **Docker Compose deployment**: Self-hosting runs through Docker Compose with PostgreSQL for data and Redis for caching and job queues, which is a genuinely small operational footprint by the standards of self-hosted marketing tools.
- **Bring your own SES account**: Self-hosted Plunk uses your own Amazon SES credentials, so per-email cost falls to SES rates and your only remaining expense is the server. At high volume this is the cheapest legitimate email path available.
- **Full data ownership**: Self-hosting means contact data, event history, and message content stay on infrastructure you control, which resolves most GDPR and residency questions by construction.
- **EU hosting on the managed service**: The hosted version is EU-hosted and GDPR compliant, so European buyers do not have to self-host purely for residency reasons.

### Developer surface

Small, documented, and the same on every plan.

- **REST API**: Full API for contacts, events, transactional sends, and campaigns, available on the free plan with no rate-limit tiering advertised.
- **SDKs**: Official Node.js and Python libraries, with plain HTTP available for everything else.
- **Every feature on every plan**: No feature tiers, no add-ons, and no capability gating. API access, custom domains, analytics, segmentation, workflows, and campaigns are included whether you pay nothing or a hundred dollars a month.
- **Webhooks**: Outbound webhooks for inbound mail and delivery events so your application can react to what happened to a message.

## Use cases

- **Indie SaaS founder consolidating two email bills**: Paying a transactional provider for system mail and a marketing tool for onboarding, with the same user existing separately in both and unsubscribes out of sync. Outcome: One contact record, one authenticated domain, one bill computed purely on volume, and an activity history that shows the receipt and the nudge email side by side.
- **Developer-led product with real activation events**: Onboarding email currently sends on a schedule regardless of what the user has done, which means telling people to complete a step they finished on day one. Outcome: Events tracked through the API drive workflows that branch on actual behaviour, and the whole thing costs a tenth of a cent per email regardless of how many contacts sit in the database.
- **Cost-sensitive team at volume**: Sending half a million emails a month and paying a per-contact marketing platform several hundred dollars for the privilege. Outcome: Self-hosted Plunk on a small server with your own SES account reduces the marginal cost to SES rates, which is roughly a tenth of what the hosted service charges and a fraction of any per-contact platform.
- **European product with data residency obligations**: Customer contracts require that personal data stay within the European Union, and most affordable email tools are US-hosted. Outcome: The managed service is EU-hosted and GDPR compliant, and if that is not enough, self-hosting inside your own infrastructure resolves the question entirely.

## Pricing

Usage-based pricing at a flat rate per email with unlimited contacts, no monthly fee, no feature tiers, and a free self-hosted option.

- **Free**: $0 per month. 1,000 emails a month; Unlimited contacts; Workflows, campaigns, segments, analytics, and API access; Custom sending domain with DKIM; Plunk branding on messages. The only difference from paid is the branding, which is a remarkably honest free tier.
- **Pay as you go**: $0.001 per email. No base fee and no minimum; Unlimited contacts at no charge; Plunk branding removed; Every feature included with no add-ons; Transactional and marketing on one bill. 100,000 emails a month costs $100. There is no contact meter to model at all.
- **Self-hosted**: $0 licence plus your own infrastructure. AGPL-3.0 licensed, full source on GitHub; Docker Compose with PostgreSQL and Redis; Bring your own Amazon SES account; Complete data ownership; No per-email fee to Plunk. Real cost is a small server plus SES rates, typically under $20 a month at moderate volume, and your own time.

Billing notes:

- Contacts are never metered on any plan. You pay only for emails sent, which is the inverse of almost every marketing email platform and materially cheaper for products with large lists and modest send frequency.
- There are no feature tiers. API access, custom domains, workflows, campaigns, segmentation, and analytics are all available on the free plan.
- At $0.001 per email, 100,000 emails a month is $100 and a million is $1,000, which is competitive with transactional providers and far below per-contact marketing platforms at equivalent list sizes.
- Self-hosting removes the per-email fee entirely; your costs become a server, PostgreSQL, Redis, and your own Amazon SES bill, which is roughly a tenth of the hosted rate at volume.
- There is no published SLA, no enterprise support contract, and no annual commitment discount, because this is an indie project rather than an enterprise vendor.

Value assessment: Plunk is the cheapest credible option in this category by a wide margin, and the pricing model is the reason. A product with 5,000 users sending four emails each a month is 20,000 emails, which costs $20 on the hosted service and effectively nothing self-hosted; a per-contact platform at that list size would charge somewhere between $50 and $250. A product with 50,000 users sending the same frequency is 200,000 emails at $200 hosted, where GetResponse, EngageBay, or HubSpot at that contact count would all charge several hundred to a few thousand. Self-hosting reduces the 200,000-email figure to roughly $20 of SES plus a small server. The thing you are giving up is not capability so much as assurance: no SOC 2, no SLA, no support contract, no multi-channel, and a hosted service run by one person. For an indie SaaS or a developer-led product, that trade is usually obviously worth making. For a company whose procurement asks for a security questionnaire, it is not.

## Strengths

- Transactional and marketing email on one contact record with one sending identity, which removes an entire category of reconciliation and reputation problems.
- Unlimited contacts with billing purely on emails sent, which is the most sensible pricing model in this category and dramatically cheaper for large lists sent to infrequently.
- Every feature on every plan with no gating, so the free tier is a complete product rather than a demonstration.
- Fully open source under AGPL-3.0 with more than 5,000 GitHub stars, so you can audit exactly what happens to your data and fork it if the project stops.
- Self-hosting via Docker Compose with PostgreSQL and Redis is a genuinely small operational footprint, and bringing your own SES account reduces marginal cost to near zero.
- The managed service is EU-hosted and GDPR compliant, which handles residency without requiring self-hosting.
- No venture funding and no growth pressure, which in practice means no repricing event and no forced migration to a tier you did not want.

## Limitations

- Email only. No SMS, no push, no in-app messaging, and no orchestration across channels, so any multi-channel programme needs a second vendor.
- No compliance certification, no SLA, and no enterprise support, which rules Plunk out wherever procurement has a checklist.
- The hosted service is operated by one person with no outside funding, which is a real continuity risk for anything in a transactional critical path.
- No landing pages, forms, popups, or lead scoring, so the acquisition side of marketing has to live somewhere else entirely.
- The email editor and template tooling are functional rather than designed, and a brand-conscious marketing team will find them thin.
- Adoption requires engineering to track events and call the API, so a non-technical team cannot start alone.
- Deliverability on the hosted service rests on shared SES infrastructure with limited reputation tooling; there is no seed testing, no inbox placement reporting, and no dedicated IP offering.

## Comparisons

- **Plunk vs Mailmodo**: Mailmodo charges $149 a month for 500 contacts and 2,000 sends and gives you interactive AMP email that Plunk cannot do. Plunk charges $0.001 per email with unlimited contacts, so the same 2,000 sends cost two dollars. Unless in-email interactivity is a measured revenue driver for your audience, the economics are not close, and Plunk also unifies your transactional path which Mailmodo does not.
- **Plunk vs Dittofeed**: Dittofeed is the other open-source answer here, aimed more squarely at customer engagement with multi-channel journeys and a stronger segmentation model. Plunk is narrower, email only, and simpler to run, with an unusually cheap hosted option. Choose Dittofeed if you want an open-source Customer.io replacement; choose Plunk if you want cheap unified email and a Docker Compose file you can actually read.
- **Plunk vs Mautic**: Mautic is the veteran open-source marketing automation platform with landing pages, forms, lead scoring, and a much larger feature surface, but it is heavy to operate and its interface shows its age. Plunk is a fraction of the operational burden and does far less. Take Mautic if you need the whole marketing apparatus self-hosted; take Plunk if you need email and workflows and nothing else.
- **Plunk vs Bento**: Bento is a hosted, event-driven lifecycle platform aimed at SaaS with genuinely good segmentation, deliverability guidance, and a managed sending posture. Plunk is cheaper, open source, and self-hostable, and it unifies transactional email. Bento is the better product for a team that wants opinionated lifecycle guidance; Plunk is the better fit for a developer who wants control and a bill measured in tens of dollars.
- **Plunk vs SuprSend**: These solve different halves of the same problem and could reasonably be used together. SuprSend orchestrates notifications across nine channels but sends nothing itself, routing through providers you supply. Plunk is one of the providers it could route through. If your problem is multi-channel fatigue and preferences, SuprSend; if it is cheap unified email with lifecycle workflows, Plunk; if it is both, run Plunk as the email provider behind SuprSend.

## Implementation

- Setup time: An hour on the hosted service to authenticate a domain, import contacts, and send. Half a day to a day for a self-hosted deployment including Docker Compose, PostgreSQL, Redis, and SES verification.
- Learning curve: Low for developers and moderate for anyone else. The concepts are small: contacts, events, workflows, campaigns, and segments. The main adjustment is thinking in events rather than lists, which is the correct habit anyway.
- Onboarding: Entirely self-serve with no sales contact on either the free or paid path, and no onboarding fee. Self-hosting is documented in the GitHub repository. There is no professional services offering, which is consistent with the price.
- Migration: Contacts import by CSV or API, but event history does not come with them, so behaviour-triggered workflows only start working for activity that happens after the switch. Authenticate your sending domain with SPF, DKIM, and DMARC before any volume, and warm gradually since the hosted service sits on shared SES infrastructure. If you plan to self-host eventually, start there rather than migrating later, because moving a live sending identity is the awkward part.

## Platform, API & security

- Platforms: Web application, REST API, Node.js and Python SDKs, Self-hosted via Docker Compose
- API: REST API covering contacts, events, transactional sends, campaigns, and segments, with official Node.js and Python SDKs and plain HTTP for everything else. Outbound webhooks for inbound mail and delivery events. API access is included on the free plan with no tiering.
- Compliance: GDPR compliant with EU hosting on the managed service, CAN-SPAM compliant unsubscribe handling
- Data residency: The managed service is hosted in the European Union. Self-hosting places all data on infrastructure you control.
- SSO: Not offered.
- Security notes: Full source available under AGPL-3.0, so the security posture is auditable rather than asserted, which is a different and in some ways stronger guarantee than a certification. There is no SOC 2 report, no penetration test disclosure, and no published SLA. Delivery runs on Amazon SES, so the underlying sending infrastructure is well understood even where Plunk's own operations are small.

## Support

- Channels: Email support, GitHub issues for the open-source project
- Documentation: Documentation covering setup, the API, workflows, campaigns, and self-hosting, plus the full source code as the ultimate reference.
- Community: More than 5,000 GitHub stars with an active issue tracker; no large forum or commercial community programme.

## Company

- Founded: 2022
- Founders: Dries Augustyns
- Headquarters: Europe
- Ownership: Independent and bootstrapped, with the product open sourced under AGPL-3.0
- Employees: Effectively one; an indie project
- Funding: No venture funding. The vendor describes Plunk as an indie SaaS with no VC backing and no aggressive growth tactics.

Timeline:

- 2022: Dries Augustyns launches Plunk as a proprietary email platform for SaaS, combining transactional sending, campaigns, and automation on one contact record.
- 2023: Adds the visual workflow builder, real-time segmentation, and custom sending domains, positioning against SendGrid and Mailgun for developer-led products.
- 2024: Transitions to a fully open-source model under AGPL-3.0 in August, publishing the source under the useplunk organisation on GitHub with Docker Compose self-hosting.
- 2025: Adds inbound email with webhook routing and settles on flat $0.001 per email pricing with unlimited contacts and no feature tiers.
- 2026: The GitHub repository passes 5,000 stars while the hosted service remains EU-hosted, unfunded, and run independently.

## Integrations

Amazon SES as the delivery layer, REST API for any language, Node.js SDK, Python SDK, Outbound webhooks for inbound mail and delivery events, Docker Compose for self-hosted deployment, PostgreSQL and Redis as self-hosted dependencies

## FAQ

### What is Plunk?

Plunk is an open-source email platform that combines transactional sending, broadcast campaigns, and visual workflow automation on a single contact record. It runs on Amazon SES, charges $0.001 per email with unlimited contacts and no monthly fee, and can be self-hosted for free under AGPL-3.0 using Docker Compose.

### How much does Plunk cost?

The free tier covers 1,000 emails a month with every feature included and Plunk branding on messages. Beyond that it is $0.001 per email with no base fee, so 100,000 emails a month is $100 and a million is $1,000. Contacts are never metered. Self-hosting costs nothing in licence fees and only your own server plus your Amazon SES bill.

### Is Plunk event-driven or list-driven?

Event-driven in a lightweight sense. You track events from your application through the API and workflows trigger from those events with delays and conditions, and segments recompute from contact data and behaviour. It is not a full customer data platform: there is no warehouse connector, no separate analytics layer, and no multi-channel orchestration.

### What does Plunk cost at 5,000 users versus 50,000?

Nothing depends on user count, which is the point. A product with 5,000 users sending four emails each a month is 20,000 emails, which is $20 hosted. A product with 50,000 users at the same frequency is 200,000 emails, which is $200 hosted. Self-hosted, the same 200,000 emails cost roughly $20 in Amazon SES fees plus a small server, because the per-email charge to Plunk disappears entirely.

### Can a marketer operate Plunk without a developer?

Partly. Campaigns, segments, and workflows are all built in the interface, so day-to-day marketing work is self-serve. What requires a developer is the foundation: contacts and events arrive through the API, and until somebody instruments your product, there is nothing for a workflow to trigger on. There are also no forms, popups, or landing pages, so the capture side needs to exist elsewhere.

### Which channels does Plunk cover?

Email, and nothing else. There is no SMS, no push notification, no in-app messaging, and no chat channel, and none are advertised as planned. If you need multi-channel lifecycle messaging, Plunk can be the email leg of it behind an orchestration layer such as SuprSend, but it will not be the whole programme.

### Who is responsible for deliverability on Plunk?

You are, substantially. You authenticate your own sending domain with SPF and DKIM, and delivery runs on Amazon SES. On the hosted service you sit on shared SES infrastructure with basic open, click, and bounce analytics but no seed-list testing, no inbox placement reporting, and no dedicated IP option. Self-hosted, you use your own SES account, which means your reputation is entirely your own and is the more defensible setup for a serious sender.

### What is self-hosting Plunk actually like to run?

Small, by the standards of self-hosted marketing tools. Docker Compose brings up the application with PostgreSQL for data and Redis for caching and job queues, and you supply your own Amazon SES credentials. The realistic ongoing cost is a modest server, an SES bill measured in cents per thousand emails, and the usual attention any production database needs: backups, upgrades, and monitoring. Compare that with Mautic, where the operational burden is the main reason people abandon it.

### Is Plunk safe to run in a transactional critical path?

The honest answer is it depends on your risk tolerance. The hosted service is operated by one person with no outside funding, no SLA, and no compliance certification, which is a real dependency for password resets and receipts. The mitigation is unusually good though: the source is fully open under AGPL-3.0, so if the hosted service ever stops, you can stand the same software up yourself with your own SES account, which is not an option any proprietary vendor offers.

### Should a five-person startup choose Plunk?

For a developer-led SaaS, it is one of the best value choices available. Unifying transactional and lifecycle email on one contact record is genuinely useful, the free tier is a complete product, and $0.001 per email with unlimited contacts is cheaper than anything else credible. The two questions to answer first are whether you need channels beyond email, in which case look at Bento, Encharge, or a notification layer, and whether procurement will ask for a SOC 2 report, in which case Plunk is disqualified before the evaluation starts.

## Editorial verdict

Plunk is the most quietly sensible piece of pricing in this whole category. Unlimited contacts, a flat tenth of a cent per email, every feature on every plan, transactional and marketing unified on one record, and a fully open-source codebase you can self-host on a Docker Compose file with your own SES account. For an indie SaaS or a developer-led product, the value is not close: a list size that would cost a few hundred dollars a month on a per-contact platform costs twenty dollars here, and self-hosting takes it lower still. The limits are real and should be stated plainly. It is email only, there is no SOC 2 or SLA, and the hosted service is run by one person with no funding, which is a genuine dependency for anything transactional. But the open-source licence is the mitigation that makes the risk tolerable, because the exit is a deployment rather than a migration. Take it if you are technical, cost-sensitive, and email is enough.

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Source: SaaSTracker (https://saastracker.org), an independent editorial project. This profile is compiled from public information, carries no peer reviews or paid placement, and was last reviewed 2026-08-22. Awards are judged on published criteria: https://saastracker.org/methodology