AISend vs Plunk
A Plunk Alternative for Flat-Priced Transactional Email
Plunk is an open-source (AGPL-3.0) email platform that combines transactional email, campaigns, and workflow automation, with a 1,000-email free plan and a paid plan at $0.001 per email with no base fee. AISend is narrower: a transactional email API with a Resend-compatible request format and flat monthly plans. Which one costs less depends on your volume — the table below shows where each wins — and if you need campaigns, automations, inbound email, or self-hosting, Plunk is the better fit.
Why Developers Switch from Plunk
- Per-email billing grows with every send: 50,000 emails is about $50/mo at $0.001 each, while AISend Pro is $14/mo flat
- The free plan is 1,000 emails/month and carries Plunk branding; AISend's free plan is 3,000/month without a footer
- Plunk uses its own request format (POST /v1/send with the HTML in body), so code written for Resend needs rewriting; AISend accepts Resend's format
AISend vs Plunk — Feature Comparison
| Feature | AISend | Plunk |
|---|---|---|
| 1,000 emails/month | $0 (Free) | $0 (Free, Plunk branding) |
| 3,000 emails/month | $0 (Free, 100/day cap) | ≈$3 (paid, $0.001/email) |
| 10,000 emails/month | $14/mo (Pro, 2,500/day cap) | ≈$10 |
| 50,000 emails/month | $14/mo (Pro, 2,500/day cap) | ≈$50 |
| 60,000 emails/month | $63/mo (Business, 5,000/day cap) | ≈$60 |
| 100,000 emails/month | $63/mo (Business, 5,000/day cap) | ≈$100 |
| Open source / self-hosting | No — hosted only | Yes (AGPL-3.0, Docker Compose) |
| Campaigns & workflow automation | No — transactional only | Yes |
| Inbound email | No | Yes (delivered as a webhook) |
| SMTP | No — REST API and SDK | Yes |
| MCP server for AI agents | Yes (aisend-mcp on npm) | Yes (@plunk/mcp on npm) |
| Recipient checks before sending | Rejects bad syntax, disposable and no-MX domains | Email validation (typos, disposable domains, missing MX) |
| Resend-compatible request format | Yes — change the base URL | No |
Where Plunk Is the Better Choice
- Open source and self-hostable — running it yourself removes the per-email fee; AISend is hosted only
- Campaigns, workflow automation, segments, and inbound email in one product; AISend only sends transactional email
- Cheaper between roughly 3,000 and 14,000 emails a month, again between 50,000 and about 63,000, where AISend's next plan is $63/mo, and above 100,000, where AISend's next plan is $149/mo (Scale, capped at 5,000/day, about 150,000/mo)
- SMTP delivery alongside the REST API
Plunk facts checked October 9, 2026 against Plunk pricing, Plunk send API reference and Plunk MCP server. Prices marked ≈ are estimates from the published per-email rate. Recheck before you buy — providers change their plans.
How to Switch from Plunk to AISend
- 1Sign up for AISend (free plan, no credit card) and create an API key
- 2Add and verify your sending domain — one domain is included on the free plan
- 3Replace Plunk's POST /v1/send call with AISend's /emails endpoint or the aisend-email SDK, renaming body to html
- 4Keep campaigns and automations on a marketing tool — AISend does not run them
- 5Point AISend's webhooks at your app, then move a small share of traffic before switching fully
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