23 Best Free Email APIs in 2026
Free email APIs are useful, but "free" is not one category.
Some providers offer a real permanent free tier. Some offer a developer sandbox. Some offer an open-source product that is free to run but still needs SMTP infrastructure. Some offer a short trial and call it free. If you choose only by the largest number in the pricing table, you will pick the wrong tool.
This guide compares 23 free email APIs and API-accessible email platforms in 2026. Sequenzy is first because it is the best starting point for SaaS teams that need transactional email, lifecycle email, subscribers, events, and marketing workflows in one product instead of a send-only API.
If you need receiving and reply parsing, read best free inbound email APIs. If you want the broader paid landscape, read best API-first email platforms.
Quick Ranking
| Rank | Tool | Free Starting Point | Best For |
|---|---|---|---|
| 1 | Sequenzy | 2,500 emails/month | SaaS transactional plus lifecycle email |
| 2 | Sender | 15,000 emails/month, 2,500 contacts | Generous free marketing email |
| 3 | EmailOctopus | 10,000 emails/month, 2,500 contacts | Simple newsletters with API access |
| 4 | Resend | 3,000 emails/month, 100/day | Clean transactional email API |
| 5 | Mailtrap | 4,000 emails/month | Testing-to-production delivery workflow |
| 6 | Loops | 4,000 sends/month, 1,000 subscribed contacts | Event-driven SaaS lifecycle email |
| 7 | Brevo | 300 emails/day | Broad suite with transactional email |
| 8 | Mailjet | 6,000 emails/month, 200/day | API and SMTP relay with basic marketing |
| 9 | Maileroo | 3,000 emails/month | Budget transactional and marketing sending |
| 10 | Mailgun | 100 emails/day | Raw email infrastructure |
| 11 | OneSignal | 10,000 email sends/month | Multichannel messaging API |
| 12 | Novu | 10,000 workflow runs/month | Open-source notification workflows |
| 13 | Knock | 10,000 messages/month | Product notification infrastructure |
| 14 | Courier | Free developer plan | Provider-agnostic notifications |
| 15 | Plunk | 1,000 emails/month or self-hosted | Open-source email platform |
| 16 | Listmonk | Free self-hosted | Newsletter and transactional API on your server |
| 17 | Buttondown | Free for first 100 subscribers | Newsletter API for small audiences |
| 18 | SMTP2GO | 1,000 emails/month | Simple SMTP/API sending |
| 19 | Postmark | 100 emails/month | Testing critical transactional email |
| 20 | Amazon SES | 3,000 message charges/month for first 12 months | AWS-native low-cost infrastructure |
| 21 | MailerSend | 500 emails/month after approval | Transactional templates and SDKs |
| 22 | SendGrid | 100 emails/day for 60 days | Trialing mature high-volume email |
| 23 | ZeptoMail | Free credit/trial, then credit packs | Cheap transactional email after trial |
Free Tier Reality Check
| Free Model | What It Means | Good Examples | Watch Out For |
|---|---|---|---|
| Permanent hosted free tier | You can keep sending at low volume without paying | Sequenzy, Sender, Resend, Mailtrap, Brevo, Mailjet, Mailgun, SMTP2GO | Branding, daily caps, low logs, support limits |
| Developer or testing tier | Enough for evaluation, not production volume | Postmark, MailerSend, SendGrid trial | Do not design production around it |
| Open-source/self-hosted | Software is free, infrastructure is yours | Listmonk, Plunk, Postal-like stacks | Deliverability, DNS, IP reputation, maintenance |
| Notification platform tier | Email is one channel inside a larger messaging API | Novu, Knock, Courier, OneSignal | May not replace a dedicated ESP |
Best Tool by Use Case
| Use Case | Best Free Starting Point | Why |
|---|---|---|
| SaaS lifecycle email | Sequenzy | Transactional, marketing, subscribers, events, automations, and analytics in one place |
| Pure transactional DX | Resend | Clean SDKs, React Email support, simple API shape |
| Free campaign volume | Sender or EmailOctopus | Large no-cost sending allowances |
| Testing and staging | Mailtrap | Built around sandbox and production delivery workflows |
| Raw infrastructure | Mailgun or Amazon SES | More control, more engineering responsibility |
| Product notifications | Novu, Knock, Courier, OneSignal | Workflow APIs across email and other channels |
| Self-hosted newsletter/API | Listmonk or Plunk | No SaaS subscription, but you own operations |
What Counts as a Good Free Email API?
A free email API should give you more than a demo endpoint.
Look for:
- Custom domain sending
- API keys and SMTP credentials
- Webhooks for delivery, bounces, complaints, opens, and clicks
- Logs while you debug setup
- Suppression handling
- Unsubscribe handling if you send marketing email
- A paid path that does not force a migration
For SaaS products, a send endpoint is rarely enough. Welcome emails, trial nudges, dunning, product updates, and receipts all touch the same user lifecycle. That is why Sequenzy ranks first: it handles more of the email system, not only the email transport.
The 23 Best Free Email APIs
1. Sequenzy
Best for: SaaS teams that want transactional email, marketing email, subscribers, events, and automations in one free starting point.
Sequenzy gives you 2,500 emails per month on the free plan with API access, transactional sending, campaigns, automations, subscribers, tags, events, and analytics. That is a better shape for SaaS than a send-only transactional API because email is connected to the customer lifecycle from day one.
A password reset is transactional. A trial-expiration reminder is lifecycle. A product update is marketing. A failed-payment notice affects revenue. Most products need all of those within the first few months. If you start with a pure API, you eventually build or buy the missing subscriber and automation layer.
Sequenzy is the right first choice when you want one system for transactional emails, Stripe integration, API-triggered events, and lifecycle email.
- Free tier: 2,500 emails/month
- API fit: Transactional sends, subscribers, tags, events, campaigns, automations, analytics
- Main limitation: Smaller ecosystem than older infrastructure providers
2. Sender
Best for: The most generous hosted free marketing-email allowance.
Sender's free plan is unusually generous: 2,500 subscribers and 15,000 emails per month with newsletters, automation, landing pages, forms, popups, and transactional emails. For small businesses and early audience building, that is a real free plan, not a token trial.
The tradeoff is branding on free emails and a less developer-native experience than Resend, Mailgun, or Sequenzy. Use it when send volume matters more than API elegance.
- Free tier: 15,000 emails/month and 2,500 subscribers
- API fit: Marketing and transactional workflows
- Main limitation: Sender branding and less SaaS lifecycle depth
3. EmailOctopus
Best for: Simple newsletters with a generous free allowance.
EmailOctopus is strong when you need low-cost list email rather than a full automation suite. Its free plan supports 2,500 subscribers and 10,000 emails per month. It also has API access for subscriber and campaign workflows.
This is not the best fit for complex product-event automation, but it is practical for founders who want a clean newsletter system and a cheap upgrade path.
- Free tier: 10,000 emails/month and 2,500 subscribers
- API fit: Subscriber and newsletter operations
- Main limitation: Basic automation compared with lifecycle platforms
4. Resend
Best for: Developers who want the cleanest transactional email API.
Resend is the best free choice when the job is "send email from code." The TypeScript SDK, React Email support, docs, and error model make integration fast.
The free plan includes 3,000 emails per month with a 100-email daily cap. Resend also supports inbound email, and inbound messages count against the same quota. That is fine for prototypes and small products, but it matters if you expect reply traffic.
- Free tier: 3,000 emails/month, 100/day
- API fit: Transactional sending, domains, webhooks, inbound, React Email
- Main limitation: Limited marketing automation depth
5. Mailtrap
Best for: Teams that want a disciplined path from sandbox testing to production delivery.
Mailtrap is useful because email testing is part of its DNA. The Email API/SMTP product has a free plan for live sending, while the sandbox product helps teams catch broken templates and accidental sends before production.
Use it when QA, staging, logs, and deliverability debugging are more important than having a full marketing automation platform.
- Free tier: 4,000 emails/month for Email API/SMTP
- API fit: SMTP, API, webhooks, delivery logs, sandbox workflows
- Main limitation: API, marketing, and sandbox are separate product areas
6. Loops
Best for: SaaS startups that want event-triggered email on a free plan.
Loops gives you up to 1,000 subscribed contacts and 4,000 sends every 30 days. The API shape is SaaS-friendly: contacts, properties, events, transactional sends, and lifecycle loops.
It is simpler than Sequenzy or Customer.io, which can be a strength for small teams. The free-plan catch is Loops branding, and the paid jump is higher than pure send APIs.
- Free tier: 4,000 sends/month to 1,000 subscribed contacts
- API fit: Contacts, events, transactional emails, SaaS loops
- Main limitation: Branding on free and lighter segmentation
7. Brevo
Best for: A broad free suite with transactional email included.
Brevo's free plan includes 300 email sends per day and supports marketing and transactional email. The contact allowance is large, so the constraint is daily sends, not list size.
That makes Brevo good for low-volume transactional email and slow-drip campaigns. It is less pleasant for a one-day launch email to a larger list because the daily cap stretches delivery.
- Free tier: 300 emails/day
- API fit: Transactional email, campaigns, contacts, automation, SMS add-ons
- Main limitation: Daily cap and broad, less developer-focused product surface
8. Mailjet
Best for: Simple API and SMTP sending with a lightweight marketing layer.
Mailjet's free plan includes 6,000 emails per month with a 200-email daily cap. It includes API, SMTP relay, webhooks, an editor, forms, and basic stats.
Mailjet is a practical option if you want both API sending and a basic campaign editor. It is not the strongest lifecycle automation tool.
- Free tier: 6,000 emails/month, 200/day
- API fit: API, SMTP, webhooks, basic campaigns
- Main limitation: Daily cap and limited automation depth
9. Maileroo
Best for: Budget transactional sending with a useful free starting point.
Maileroo offers a free email API plan with monthly sending included and paid tiers that stay inexpensive. It is worth considering if you want a smaller provider with simple SMTP/API sending and analytics.
It does not have the ecosystem depth of SendGrid, Mailgun, or Resend, so evaluate docs, support, and logs before using it for critical authentication email.
- Free tier: 3,000 emails/month
- API fit: SMTP relay, email API, transactional and marketing sending
- Main limitation: Smaller provider and ecosystem
10. Mailgun
Best for: Raw email infrastructure, inbound routing, and flexible webhooks.
Mailgun's free plan includes 100 emails per day, API and SMTP sending, webhooks, one sending domain, two API keys, one inbound route, and short log retention.
This is a strong developer option if you want infrastructure primitives. You get control, but you also build more of the product layer yourself.
- Free tier: 100 emails/day
- API fit: Sending, SMTP, webhooks, inbound routes, analytics
- Main limitation: Short logs and no full marketing layer
11. OneSignal
Best for: Apps that treat email as one channel in a broader notification system.
OneSignal is better known for push notifications, but it also exposes email through its messaging API. The free plan includes monthly email sends, and the API can manage users, subscriptions, segments, and cross-channel messaging.
Use OneSignal when mobile push, in-app, SMS, and email belong together. Do not choose it as a pure email deliverability tool unless the multichannel layer is the point.
- Free tier: 10,000 email sends/month
- API fit: Email, push, SMS, in-app messaging, users, segments
- Main limitation: Email is one channel, not the whole product
12. Novu
Best for: Open-source notification workflows with email as a channel.
Novu gives developers a workflow engine across email, in-app, SMS, chat, and push. The free cloud plan includes workflow runs, and the project is open source.
Novu is not a classic ESP. It orchestrates notifications and connects providers. If you want a unified notification layer, it is useful. If you want a deliverability-first email service, pair it with a provider underneath.
- Free tier: 10,000 workflow runs/month
- API fit: Notification workflows across multiple channels
- Main limitation: Requires provider choices and workflow design
13. Knock
Best for: Product notification infrastructure.
Knock has a developer plan with 10,000 messages and supports multichannel notification workflows. It is strong for product notifications, preference management, batching, delays, and user-facing notification systems.
It is not the cheapest path after free, but the product is well-shaped if notifications are a core feature in your app.
- Free tier: 10,000 messages/month
- API fit: Workflows, broadcasts, guides, preferences, multichannel notifications
- Main limitation: Paid jump can be steep for small teams
14. Courier
Best for: Routing messages through multiple providers from one API.
Courier abstracts notification delivery across channels and providers. That can be useful if you want email, SMS, push, and chat from one API while swapping providers underneath.
The tradeoff is abstraction. You gain one interface, but you may lose some direct control over provider-specific email behavior.
- Free tier: Free developer plan
- API fit: Provider routing, notification design, multichannel delivery
- Main limitation: Abstraction can hide email-specific details
15. Plunk
Best for: Open-source email with a simple hosted free tier.
Plunk combines transactional email, campaigns, workflows, analytics, and custom domains. It also has an open-source version for teams that want to self-host.
The hosted free plan is useful for small projects, while self-hosting removes platform subscription cost but puts deliverability on you.
- Free tier: 1,000 emails/month hosted; self-hosted software is free
- API fit: Transactional, campaigns, workflows, contacts
- Main limitation: You own more operations if self-hosted
16. Listmonk
Best for: Self-hosted newsletters and transactional messages.
Listmonk is free and open source. It has an API, campaign management, lists, templates, and a transactional message API. It is very fast and can run cheaply.
The catch is that it is not an email delivery provider by itself. You still need SMTP infrastructure such as SES, Postmark, Mailgun, or another relay.
- Free tier: Free self-hosted software
- API fit: Lists, campaigns, subscribers, transactional messages
- Main limitation: Requires hosting and SMTP delivery
17. Buttondown
Best for: Newsletter API workflows for very small audiences.
Buttondown is a simple newsletter platform with API access available on all plans, including free. The free tier covers the first 100 subscribers.
Use it for developer-friendly newsletters, not product-event lifecycle automation.
- Free tier: First 100 subscribers
- API fit: Newsletter publishing, subscribers, archives
- Main limitation: Small free audience and newsletter-focused scope
18. SMTP2GO
Best for: Simple SMTP/API sending that does not try to be a marketing suite.
SMTP2GO offers 1,000 emails per month on its free plan. It is practical for internal apps, side projects, and low-volume transactional sending.
The hourly and daily limits matter. Do not use it for batch campaigns unless the volume is tiny.
- Free tier: 1,000 emails/month
- API fit: SMTP relay, API, reporting, bounce handling
- Main limitation: Low-volume and less modern workflow tooling
19. Postmark
Best for: Testing a high-quality transactional provider before paying.
Postmark's free Developer plan includes 100 emails per month. That is not a production free tier, but it is enough to test message streams, templates, inbound processing, and the API.
Postmark is excellent when the email is critical: password resets, magic links, receipts, invoices, and security notifications.
- Free tier: 100 emails/month
- API fit: Transactional send, templates, message streams, webhooks, inbound
- Main limitation: Free volume is tiny
20. Amazon SES
Best for: AWS-native teams optimizing for cost after the free period.
Amazon SES has API and SMTP sending, inbound receiving, events, IAM controls, and AWS-native integrations. The free tier provides message charges for the first 12 months after starting SES, but it is not a permanent hosted free plan.
SES is cheap at scale, but you build the product layer: templates, approvals, logs, suppression UI, unsubscribe handling, and analytics.
- Free tier: 3,000 message charges/month for first 12 months
- API fit: SMTP, API, inbound, AWS events
- Main limitation: Infrastructure-heavy and time-limited free tier
21. MailerSend
Best for: Low-volume transactional template testing.
MailerSend has a modern transactional API, SMTP relay, templates, webhooks, SDKs, and inbound routing. The free plan is tight now, so treat it as a testing plan rather than a generous startup tier.
It is still useful when non-developers need to edit templates and developers trigger them through an API.
- Free tier: 500 emails/month after approval
- API fit: Transactional API, SMTP, templates, webhooks, inbound routing
- Main limitation: Tight free quota
22. SendGrid
Best for: Trialing a mature enterprise email API.
SendGrid is mature, scalable, and widely integrated. The catch is that its current free Email API offer is a trial: 100 emails per day for 60 days.
Use it when your organization already expects Twilio SendGrid or when you want to evaluate a high-volume platform before paying. Do not treat it as a permanent free tier.
- Free tier: 100 emails/day for 60 days
- API fit: Transactional sending, templates, contacts, event webhooks
- Main limitation: Trial-based, not long-term free
23. ZeptoMail
Best for: Very cheap transactional email after a short evaluation.
Zoho ZeptoMail is transactional-only and supports SMTP plus email API integration. It offers a free credit/trial path, then uses inexpensive email credits.
It is not the best permanent free plan, but it can be a very low-cost option once you are past the trial.
- Free tier: Free credit/trial, then paid credits
- API fit: Transactional email API and SMTP
- Main limitation: Not a long-term free tier
Final Recommendation
Use Sequenzy first if you are building a SaaS product and want free email API access plus the rest of the lifecycle email system: subscribers, events, campaigns, automations, transactional sends, and analytics.
Use Resend if you only want the cleanest transactional send API.
Use Sender or EmailOctopus if free campaign volume matters most.
Use Mailgun, SES, or SMTP2GO if you want infrastructure control.
Use Novu, Knock, Courier, or OneSignal if email is one channel inside a broader notification system.
The mistake is choosing based on free volume alone. Pick the API that matches the workflow you will still need six months from now.