Deliverability-first email API that 150K+ developers trust. 24/7 expert support.
curl -X POST "https://send.api.mailtrap.io/api/send" \
-H "Authorization: Bearer $MAILTRAP_API_KEY" \
-H "Content-Type: application/json" \
-d '{
"from": {"email": "hello@yourdomain.com", "name": "Your App"},
"to": [{"email": "user@example.com"}],
"subject": "Welcome!",
"text": "Thanks for signing up."
}'
RESTful endpoints to send transactional and bulk emails, to manage templates, suppressions, your account and get delivery statistics – all from a single, well-documented API.
/send
Send transactional emails
/bulk
Send promotional emails
/templates
Create and manage email templates
/stats
Track delivery, open, click, and bounce rates
/suppressions
Manage bounces and unsubscribes
import { MailtrapClient } from "mailtrap";
const client = new MailtrapClient({
token: process.env.MAILTRAP_API_KEY,
});
async function sendEmail() {
await client.send({
from: {
email: "sender@example.com",
name: "Sender Name"
},
to: [{ email: "recipient@example.com" }],
subject: "Hello from Mailtrap",
text: "Welcome to Mailtrap!",
html: "<h1>Welcome to Mailtrap!</h1>"
});
}
sendEmail();Integrate email API into your stack: native support for modern dev tools and AI coding assistants.
Send onboarding flows, billing notifications, and feature updates.
Send transaction confirmations, security alerts, and market updates.
Send booking confirmations, payment receipts, and promotional offers.
Send welcome emails, feedback requests, and progress updates.
Mailtrap is the reliable platform that handles our email delivery with rapid sending times and high inboxing rates. This frees me up to focus on growing the business, not debugging email issues.
High deliverability with every plan. Upgrade for dedicated IPs, extended logs, and priority support.
To try out Mailtrap
For startups and small businesses
For growing businesses
For organizations that send at scale
The send endpoint is for transactional emails (e.g., password resets, alerts), while the bulk endpoint is for marketing and promotional content.
Both share the same API structure, but use different infrastructure and host URLs to isolate sending reputation and maintain high deliverability.
We enforce a general rate limit of 150 requests per 10 seconds per API token.
Specific APIs have additional account-level limits, such as the Contacts API (200 requests/60s) and Stats/Suppressions APIs (10 requests/60s).
Exceeding these limits triggers a 429 Too Many Requests error.
For optimal performance, implement exponential backoff, distribute requests evenly to avoid bursts, and cache responses where possible.
Yes. You can add and verify multiple sending domains and subdomains within a single Mailtrap account.
Each domain requires independent DNS verification and a compliance check before it reaches Verified status; emails cannot be sent from Pending or Rejected domains.
For better security, use the Organizations feature to group domains or create unique API tokens for specific environment isolation.
Note that unsubscribes are domain-specific. If a recipient unsubscribes from one domain, the system will only reject future messages from that specific domain, allowing you to continue sending to them from other verified domains or subdomains in the same account.
A single request supports up to 1,000 recipients per field (to, cc, and bcc). If you are using the batch endpoint (/api/batch), you can send up to 500 individual messages per API call.
Each of those 500 messages retains the same 1,000-recipient limit per field, allowing for efficient high-volume distribution within a single payload.
Log and body retention periods depend on your subscription tier:
Logs include historical email data and event history, while body retention refers to the ability to preview the specific content of the sent message.
An email API abstracts away SMTP complexity by accepting HTTP API requests and handling email delivery infrastructure on the provider’s side. It includes the SMTP relay, DNS resolution, retry logic, and deliverability management.
So, when choosing an email API for developers, you’re really choosing two things:
The sections below break down what to evaluate when comparing the best email APIs for your use case.
An API is worth your time, only if it delivers emails reliably. Therefore, you need to focus on
IP reputation, authentication setup, stream separation, and failure handling determine whether your email lands in the inbox.
For a deeper dive, see our guide on inbox placement, and here, you can check a quick breakdown of the most critical features. And here’s a quick breakdown of key features.
Shared IPs pool your sender reputation with other senders, so one spammer in the pool can tank your deliverability. Now, this doesn’t mean shared IPs don’t work at all. If you send under ~100K emails a month, shared IPs are a better choice than a dedicated IP address. However, you need to be sure that the provider actively monitors pool healtth and removes bad actors quickly.
On the other hand, dedicated IPs give you full control. They require warm-up, though: gradually ramping email volume so ISPs build trust. Doing this manually can be a pain unless you have an experienced team, so look for providers that offer automated IP warmup, ideally with some load balancing in the first months.
Check for:
Mailtrap offers dedicated deliverability experts starting from Business plan to assist with scaling and volume transitions.
SPF, DKIM, and DMARC setup is usually documented in domain verification guides. Review these before signing up to understand the configuration burden.
Look deeper:
If you send transactional emails, bulk emails, and marketing emails, verify they’re routed through separate infrastructure. Bulk email campaigns carry higher complaint risk and require a straightforward unsubscribe option.
This is the setup you want: Mailtrap’s transactional email service, for instance, separates transactional and bulk into distinct streams with isolated reputation.
Check for:
Understand how the provider handles temporary and permanent failures. For more on feedback loops and bounce processing, see our dedicated guide.
Check for:
Major blocklists like Spamhaus, Barracuda, or SpamCopcan impact any sender. The question is whether the provider monitors proactively and alerts you.
Mailtrap includes proactive blocklist monitoring with deliverability alerts as part of its infrastructure.
Product growth drives email growth: more users, more signups, more triggered messages. High-volume email sending requires careful evaluation of rate limits and throttling.
Every email API service for developers enforces rate limits, but how they’re structured varies.
Check both:
Keep in mind that “High throughput” is marketing, not a spec; and Mailtrap, for example, documents rate limits transparently.
Email throttling controls the rate of outbound SMTP traffic (messages and connections per time unit) from your sending infrastructure to recipient mail servers.
Check:
Aggressive sending, without throttling, triggers rate limiting on the receiving end, which hurts deliverability. Look for providers that offer a flexible email API, basically a configurable throttling or intelligent auto-throttling based on recipient domain feedback.
If you send bulk email campaigns or digests, check batch capabilities.
Check for:
The developer experience layer determines how fast you integrate the service and how easily you debug and troubleshoot. Here’s what to look at.
Check which programming languages the provider officially supports and how actively SDKs are maintained.
Check for:
Mailtrap provides actively maintained Mailtrap SDKs for Python, Node.js, PHP, Ruby, Java, and Elixir.
Evaluate the API structure itself. This affects how cleanly email sending API functionality integrates into your codebase. For a comparison of approaches, see SMTP vs Email API.
Check for:
API documentation is where you’ll spend time when things break. Evaluate it like you’d evaluate the code.
Check for:
Mailtrap provides quickstart guides with copy-paste code samples for all supported languages and a complete API reference with documented error codes
Measure how long it takes from signup to a delivered email. This indicates onboarding friction and documentation quality.
Check for:
When API calls fail, the response determines how fast you diagnose and fix.
Check for:
Additionally, inspect how the provider handles audit logs, for instance:
Mailtrap provides audit logs on the Enterprise plan.
Hype tip: Check if the email API service supports AI-native integrations and provides an MCP server.
Logs and email analytics show delivery status, failures, and engagement. The depth and retention of this data determines how fast you diagnose problems when they arise.
Check what data is logged and how long it’s retained.
Check for:
Mailtrap retains email logs for up to 30 days on higher tiers, including full body content with HTML preview and spam analysis.
When you’re debugging, you need to find specific emails fast.
Check for:
Tip: Test the log search with realistic queries before committing.
Beyond individual email logs, you need aggregate metrics to monitor sending health.
Check for:
Note that open and click tracking require pixel/link injection. Confirm this is configurable and understand the privacy implications for your use case.
And, with Mailtrap you get:
Webhooks are critical for automation and monitoring workflows because they push event data to your systems in real-time.
Check for:
Mailtrap supports webhooks for all major events with documented payload schemas and retry logic.
Proactive alerts surface problems before they escalate.
Check for:
Heads-up: If the provider doesn’t offer configurable alerts, you’ll need to build monitoring on top of webhooks yourself. Factor that engineering cost into evaluation.
Keep in mind that the real comparison is the total cost of ownership. Here’s how to view it.
And here’s what to pay attention to.
Understand how the provider charges before comparing numbers.
Common models:
Pro Tips:
What happens when you exceed your plan limit matters more than the base price.
Check for:
Check certifications and access controls early, not after integration is complete. Why? Compliance gaps discovered late mean rework or starting over.
Certifications signal that a provider meets established security standards. Check which ones matter for your business needs.
Common certifications:
Ask for certification documentation upfront. “We’re SOC 2 compliant” means nothing without the audit report. Mailtrap is ISO 27001 certified and SOC 2 compliant, with documentation available at Trust Center.
Beyond certifications, check alignment with regulations relevant to your business.
Key regulations:
Request the provider’s DPA and review data processing terms. If legal review is required before signing, factor that timeline into your evaluation.
Check how data is protected in transit and at rest.
Check for:
If your security team requires specific encryption standards, confirm compatibility before integration.
Evaluate how the provider handles authentication and authorization for your team.
Check for:
Granular access controls reduce blast radius if a key leaks. If the provider only offers full-access API keys, you’re one compromised key away from total account access.
Check how the provider handles security incidents and breaches.
Check for:
The quality of customer support determines whether you resolve issues in hours or days. And if you’re switching from another provider, migration support can mean the difference between a smooth transition and weeks of deliverability problems.
Check how you can reach the support team and when they’re available, including.
For example, Mailtrap offers 24/7 support from the email deliverability team with priority response starting from Business plan.
First-time setup is where most issues occur. Check what help is available during integration, including.
Available onboarding support saves debugging hours and Mailtrap provides onboarding assistance for customers on Business plan or above.
Switching email service providers isn’t just API integration. It’s DNS changes, IP warm-up, reputation transfer, and potential deliverability dips.
Check for:
Mailtrap offers dedicated migration support including DNS guidance, warm-up planning, and deliverability monitoring, as well as step-by-step migration tutorials:
Choosing an email API service provider is choosing the infrastructure. The API interface (endpoints, SDKs, documentation) is what you interact with daily. But what determines whether your emails reach the inbox is everything behind it: IP reputation, authentication handling, retry logic, and stream separation.
Evaluate both layers:
Don’t evaluate a transactional email API service for developers on docs alone. Send test emails. Trigger errors intentionally and inspect responses. Ask support technical questions and measure response time and quality. Check GitHub for SDK maintenance. These signals tell you more than marketing pages.
If you’re evaluating Mailtrap Email API: dedicated IPs from 100k/month with automatic warm-up, separate transactional and bulk streams, 30-day log retention, 24/7 support with deliverability experts starting from Business plan. Free plan includes 4,000 emails/month.
Useful links:
GitHub SDKs:
Step-by-step tutorials on how to send emails with REST API:
