If you're building a SaaS product, mobile app, website, or internal tool, email usually becomes a requirement sooner than expected.
Password resets, verification codes, welcome emails, invoices, notifications, receipts, product updates — eventually, your application needs a reliable way to send all of them.
That's where email APIs come in.
Instead of maintaining your own SMTP infrastructure, an email API gives your application a simple interface for sending messages while the provider handles the underlying delivery infrastructure, authentication, bounces, reputation, and reporting.
The good news is that you don't necessarily need to pay to get started.
Several email providers offer free plans or free developer tiers. The important part is understanding what "free" actually means: some offer a permanent monthly allowance, some impose daily limits, some are primarily designed for testing, and others give you inexpensive infrastructure rather than a complete email platform.
We've compared seven options worth considering in 2026.
What makes a good free email API?
A free email API isn't particularly useful if it only gives you a few test messages and then forces you to migrate somewhere else.
When evaluating free email services, it's worth looking at more than the number of emails included.
Some of the things we considered include:
Custom domain support
REST API availability
SMTP support
Email templates
Delivery tracking
Webhooks with cryptographic signature verification
Bounce and complaint handling
Developer experience
Daily versus monthly limits
Whether the free tier is permanent or time-limited
How easy it is to move to a paid plan later
With that in mind, here are seven options worth looking at.
1. Mailofly
Best for: developers and small teams that want API + SMTP + email management in one platform
Mailofly is a developer-first email delivery platform designed around both transactional and marketing email.
The free plan currently includes 3,000 emails per month, with a generous daily allowance, and doesn't require a credit card. It includes REST API access, universal SMTP relay, email templates, delivery tracking, custom sending domains, and 15 days of searchable log retention.
That makes it useful for everything from a small SaaS application sending authentication emails to a startup running product notifications and marketing broadcasts.
The API is designed to stay relatively straightforward: create an API key, verify your domain with automated DNS records, and start sending through the REST API or SMTP.
Free Plan Details:
3,000 emails/month free forever
200 emails/day allowance
Custom verified sending domain
Full REST API & SDKs (Node.js, Python, Next.js, Go, PHP)
Universal SMTP Relay (Ports 587 & 465)
15-day searchable delivery logs
Multi-provider failover routing (AWS SES, Mailgun, SendGrid fallback)
Official MCP Server for AI coding agents
No credit card required
One thing that makes Mailofly particularly interesting is that it isn't limited to being an API-only transport layer. The platform also includes native campaign sequences, contact management, responsive templates, automated email warmup, and team-oriented email workflows.
That means you can start with transactional email and gradually use the same platform for product sequences instead of introducing another provider.
Potential downside: Mailofly is a newer platform compared with established legacy giants such as Amazon SES, so its community ecosystem is growing.
Try Mailofly REST Email API for Free | Connect via Mailofly SMTP Relay
2. Resend
Best for: developers who want a simple transactional email API
Resend has become popular among developers building modern web applications, particularly applications using JavaScript, TypeScript, React, and Next.js.
See how Mailofly compares: Mailofly vs. Resend In-Depth Comparison.
Its API is deliberately simple, and the platform has strong support for developer-oriented workflows.
The current free plan provides 3,000 emails per month, with a 100-email daily limit, and includes one custom domain.
Free Plan Details:
3,000 emails/month
100 emails/day cap
1 domain
REST API access
1-day log retention on free tier
React Email template support
Resend is particularly appealing if your main requirement is transactional email from application code.
The tradeoff is that Resend's product is strictly oriented toward application transactional email rather than cold outreach or contact marketing.
Potential downside: The 100-email daily limit can become restrictive quickly for applications with growing user signups, and log retention is limited to 24–72 hours on basic tiers.
3. Brevo
Best for: teams that need both transactional and marketing email
Brevo (formerly Sendinblue) takes a broader approach than a typical developer-focused email API.
Alongside transactional email, it provides campaign management, contacts, automation, SMS, and other CRM features.
Its free plan is permanent and currently allows 300 email sends per day, with support for unlimited contacts.
Free Plan Details:
300 emails/day (approx. 9,000 emails/month)
Unlimited contact storage
Transactional email & marketing campaigns
REST API & SMTP relay
The daily limit is the important thing to understand. At 300 emails per day, you could theoretically send around 9,000 emails in a 30-day month, but the quota resets daily and unused sends don't roll over. Brevo also adds its branding logo to emails sent on the free plan.
Potential downside: Developers looking for a minimal, API-first experience may find Brevo bloated and slower than modern developer APIs.
4. Mailgun
Best for: developers who want established email infrastructure
Compare features and free tier limits in our Mailofly vs. Mailgun In-Depth Comparison.
Mailgun has been around for years and is heavily focused on developer-oriented email infrastructure.
Its trial free plan includes 100 emails per day for 30 days, one custom sending domain, REST API access, SMTP relay, tracking, analytics, and webhooks.
Free Plan Details:
100 emails/day
1 custom sending domain
REST API & SMTP relay
Tracking, analytics, and webhooks
1-day log retention
Mailgun is useful when email is fundamentally an infrastructure problem for your application rather than primarily a marketing workflow.
Potential downside: Mailgun has transitioned mostly away from a permanent free tier toward paid plans starting at $35/mo. The 100-email/day limit makes it suitable only for development sandboxing.
5. Mailjet
Best for: API and SMTP sending with a simple marketing layer
Mailjet is another established email service (part of Sinch along with Mailgun) that combines developer infrastructure with campaign-oriented functionality.
Its free plan currently includes 6,000 emails per month, with a 200-email daily limit. It also provides API access, SMTP relay, webhooks, an email editor, and basic statistics.
Free Plan Details:
6,000 emails/month
200 emails/day
Unlimited contacts
REST API & SMTP relay
Visual drag-and-drop email editor
The relatively large monthly allowance makes Mailjet useful for small applications that don't need to send large batches at once.
Potential downside: The 200-email daily cap can become a bottleneck during traffic spikes or product announcements.
6. Postmark
Best for: testing transactional email
Looking for lower volume pricing? Read our Mailofly vs. Postmark Comparison.
Postmark takes a different approach from many other providers. Rather than offering a large free allowance, Postmark provides a 100-email-per-month free Developer plan with no expiration.
Free Plan Details:
100 emails/month total
Developer test plan
No expiration date
Transactional email infrastructure
That isn't enough for production applications, but it is enough to evaluate the platform or test transactional email integration before committing to a paid plan ($15/mo for 10k, $55/mo for 50k).
Potential downside: 100 emails per month is the smallest allowance on this list, and Postmark strictly prohibits any cold email or outbound marketing.
7. Amazon SES (Simple Email Service)
Best for: high-volume senders comfortable with AWS infrastructure
Amazon SES is the bedrock infrastructure that many other email providers build on. It offers raw SMTP and REST API endpoints at extremely low cost.
Under the AWS Free Tier, you can send up to 3,000 emails per month free for the first 12 months when calling SES from an application hosted on Amazon EC2 or AWS Lambda.
Free Plan Details:
3,000 emails/month (from EC2/Lambda for first 12 months)
Extremely low pricing afterwards ($0.10 per 1,000 emails)
REST API & SMTP relay
Potential downside: Amazon SES is notoriously developer-unfriendly to set up. You start in a strict sandbox where you can only send to verified addresses. You must manually configure bounce/complaint handling via Amazon SNS and SQS, and requesting production access requires submitting a detailed ticket to AWS support.
Comparing Free Email API Limits & Quotas
One of the easiest mistakes when comparing email APIs is looking only at the largest number in the "free" column.
For example:
3,000 emails/month sounds larger than 300/day, but 300/day actually equals 9,000 emails over 30 days if your traffic is spread evenly.
A 100-email/day limit will block your application if you have a spike of 150 signups in a single afternoon.
A 100-email trial (like Postmark) isn't equivalent to a permanent monthly free tier.
AWS credits aren't the same thing as a permanent free email allowance.
That's why the right choice depends heavily on how your application generates email volume.
Which Type of Email API Do You Need?
Building a SaaS or Modern Web Application
Look for a developer-focused API with fast HTTP response times, signed webhooks, automatic SPF/DKIM verification, and a straightforward upgrade path.
Mailofly and Resend are the leading options for developers building with modern stacks like Next.js and Supabase.
Sending Marketing Campaigns & Broadcasts
A platform such as Mailofly or Brevo makes more sense because campaign management, contact segmentation, and unsubscribe tracking are built into the product rather than something you need to build yourself.
Already Heavily Invested in AWS
Amazon SES can be a natural choice if your infrastructure already lives inside an AWS VPC and your team has the DevOps bandwidth to manage SNS queues and sandbox requests.
What to Check Before Choosing an Email API
The free sending allowance is only one part of the decision. Before putting an email provider into production, check these eight criteria:
Domain Authentication: Does the provider support SPF, DKIM (2048-bit), and DMARC configuration for your sending domain?
Daily Limits: A provider offering 3,000 emails per month may still block your app if the daily limit is capped at 100.
Webhooks: Can your application receive cryptographically signed events for delivered, bounced, complained, opened, or clicked emails?
Log Retention: How long can you access raw message events when debugging an email that didn't arrive? (Mailofly provides 15–30 days; competitors often provide only 1–3 days).
SMTP Fallback: If you have existing software (like WordPress or Postfix) that doesn't support the provider's REST API, universal SMTP relay support saves you from rewriting your integration.
Templates: Check whether templates can be created via React Email, raw HTML, or managed through a dashboard editor.
Multi-Provider Failover: Does the provider have redundant sending routes if an upstream provider degrades?
Upgrade Path: Is moving to the next tier cost-effective? (Check cost per 1,000 emails beyond the free tier).
Final Verdict: Which Free Email API Should You Choose?
The right choice depends on your architecture:
Choose Mailofly if you want 3,000 free emails/month, both REST API and SMTP access, 15-day searchable logs, multi-provider failover, and an official MCP server for AI agents.
Choose Resend if your only priority is application transactional email in a pure React/Next.js environment.
Choose Brevo if you need marketing campaigns, contacts, and SMS along with your transactional email.
Choose Mailgun if you're looking for established legacy infrastructure and don't mind upgrading quickly to a paid tier.
Choose Postmark if you want a small test allowance (100 emails) to evaluate high-reputation transactional delivery.
Choose Amazon SES if you have dedicated DevOps engineers and want raw, rock-bottom cost inside AWS.
Ready to get started? Create a free Mailofly account in 30 seconds and start sending with your custom domain today.
