6 Best Email API Services For Developers Tested & Compared: Here’s What I Found

On July 28, 2025
23min read
Ivan Djuric, an author at Mailtrap
Ivan Djuric Technical Content Writer @Mailtrap
Best email APIs

Considering the size of the industry nowadays, I have to say that looking for the best email API (application programming interface) is like searching for a needle in a haystack.

So, I’ve spent the past few weeks going through the haystack of email APIs, then I reviewed the best of them and compiled a nice little list to help you choose the best one for your needs.

Before we dive in, if you feel like freshening up or fine-tuning your knowledge, you can check out the article our email infrastructure expert, Dzenana, has written on email APIs.

Best email API: a snapshot

Click on a platform name to jump ahead to the detailed review.

  • Mailtrap is best for high-volume product companies that are looking for high deliverability rates, in-depth analytics, and growth-focused features.
  • Mailgun is best for developer teams who need detailed logs and an email validation API on top of an email API.
  • SendGrid is best for enterprise users who need granular control over their user permissions.
  • Amazon SES is best for current AWS users who have extensive experience with delivering emails.
  • Postmark is best for teams looking to send transactional emails and don’t need any extra features.
  • Resend is best for developer teams who are using JS stack and need to create dynamic email templates.

I’ve made a chart to help you compare the APIs you might be leaning towards. Check it out.

Email APIFree planPricingIntegration
Mailtrap3,500 per monthFrom $15Node.js, PHP, Ruby, Python, Elixir, Java
Mailgun100 per dayFrom $15Python, Go, Node.js, PHP, Java, Ruby
SendGrid100 per dayFrom $19.95C#, Go, Java, Node.js, PHP, Python, Ruby
Amazon SES3,000 per month (during the first year)$0.10 per 1,000 emailsJava, .NET, PHP, Python, Ruby, Go
PostmarkN/AFrom $15Ruby, RoR, .NET, Java, PHP, Node.js
Resend3,000 per monthFrom $20Node.js, PHP, Laravel, Python, Ruby, Go, Java, Rust, .NET

Disclaimer: The ratings, features, and prices are up-to-date as of writing this article, but they could be different when you’re reading it, as they’re prone to change.

Email API providers comparison methodology

To bring you an unbiased, accurate, and comprehensive review of the best email API providers, I conducted a thorough research and tested (almost) everything they offer.

However, I must note that I didn’t conduct the research alone, since I had the help of Mailtrap deliverability experts, security team, and developers who work on our infrastructure.

Documentation research

First and foremost, I made sure to dig through each provider’s:

  • Official API docs to see how easy to integrate for your team an API is and what it offers (e.g., sending endpoints, bounce handling, templates, etc.).
  • GitHub repositories to check whether an API is being regularly maintained and updated.
  • Testimonials and reviews to see what a provider’s user base thinks and how the APIs hold up compared to advertisements. 
  • Knowledge bases and blogs to look for helpful guides and tutorials on setting up and using an API.

Hands-on testing

Recently, over at Mailtrap, we conducted a thorough email API flexibility research where we:

  • Sent emails with different sending configurations to test real-world use cases such as sending attachments and bulk emails, etc.
  • Triggered API rate limits and retry behavior to inspect how an API handles high volume, throttling, and retries.
  • Created email templates to evaluate how much personalization each API allows and to test templating logic and dynamic content.
  • Set up webhooks for some of the events they support to see how quickly you get automated notifications about the most important metrics like bounces.
  • Used the testing solutions (if any) to validate email designs, check spam scores and rendering across clients, test authentication headers, etc.

Now, let’s get on with the reviews of each email API provider or check out the detailed criteria first by clicking on this jump link

Best email API: Mailtrap

G2: 4.8 🌟 Capterra: 4.8 🌟

Mailtrap Email Delivery Platform is designed for SaaS teams or product companies with high sending volumes that need high deliverability rates, in-depth analytics, and growth-focused features. 

Additionally, Mailtrap offers one of the most flexible email APIs out there that allows developer teams to fine-tune their sending configuration according to their specific needs. Of course, I would never claim this without being able to back it up.

Recently, we’ve performed numerous tests with the top APIs in the industry, simulating real-world usage to see how much control the user gets. Here’s a table that summarizes key findings of our research:

Dedicated IPsAvailable from 100k emails/month with auto warm-up. 
Separate streams✅ Bulk and transactional
Rate handling✅ No limits, customizable throttling
Webhooks✅ Full events + logs
Templates✅ Handlebars
Testing✅ Full Sandbox + API
Customer supportTicket, chat, priority support

To learn more about our methodology and get more in-depth information on technical tidbits like IP infrastructure, throttling, retry mechanisms, etc., read our full comparison

Why is it the best email API?

  • High deliverability

Mailtrap uses separate sending streams, dedicated IP addresses, email warm-up, throttling, and other advanced features to help all of its users achieve high deliverability rates, regardless of the plan. 

The platform also has a team of deliverability experts at its users’ disposal, who can help you with any deliverability-related issues you might face.

Moreover, we’ve recently performed several deliverability tests with top API providers. To make sure the tests were fair to everyone, we used free plans, didn’t warm up domains, used the same template, etc. 

Here’s how Mailtrap performed:

PlatformEmail placement resultsSpam filter ratingInbox email delivery with top providers
MailtrapInbox: 78.8%
Tabs: 4.8%
Spam: 14.4%
Missing: 2.0%
Google Spam Filter: Not spam; Not phishy
Barracuda: Score 0
Spam Assassin: Score: -3.8
Gmail: 67.50%
Outlook: 77.78%
Hotmail: 100%
Yahoo: 55.56%
Source
  • In-depth analytics

With Mailtrap, you can keep an eye on the performance of your email campaigns thanks to helicopter view dashboards and drill-down reports. These let you track email metrics like opens, clicks, bounces, and others. 

Additionally, Mailtrap will keep your email logs for up to 30 days,

  • Email templates

Besides the drag-and-drop email builder, which can make your marketers’ lives easier, Mailtrap offers an HTML editor your devs can use to create email templates from scratch.

The templates use the Handlebars engine with which you can set up additional variables and conditional variables like if and else statements to automate a big portion of your sending workflow.

Most importantly, you can integrate the templates with the API or even SMTP, so you can test them via the Sandbox and then forward them after making sure they’re pitch-perfect.

Pricing

Mailtrap offers several different scalable plans and has one of the most cost-effective email APIs since it doesn’t keep customer support or high inboxing rates locked away for higher tiers.

As of writing this article, the most popular plan is Business 100k, being in the golden middle and offering a plethora of advanced features with 100,000 monthly emails at an affordable rate.  

Here’s a quick table that sums the pricing plans up:

PlanMonthly costEmail limitKey features
Free $0Up to 3,500 emailsSMTP relay,
SMTP API,
drag-and-drop editor,
webhooks
Basic From $1510,000+ emailsEmail logs (5 days),
body retention,
click-rate tracking,
HTTPS link branding
Business (the most popular)From $85100,000+ emailsEmail logs (15 days),
dedicated IP,
auto warm-up
Enterprise From $7501,500,000 emailsAll of the above +
priority support and 30 days email log retention
CustomCustomFrom 1,500,000All of the above

For more details, please consult the official Mailtrap pricing page.

Pros

Cons

  • Currently, you can only integrate Mailtrap with services such as Zapier and Tabular email, but more integrations are on the way.
  • Automations are still in alpha but the official release is planned for the near future.

Developer experience

Official API documentation

Mailtrap offers easy-to-use SDKs for Node.js, PHP, Ruby, Python, Elixir, and Java.

It offers code snippets for major programming languages, which lets you start sending emails right away. All you need to do is copy/paste the provided script into your sending configuration, insert your credentials, and you’re off.

Here’s a Node.js code snippet offered by Mailtrap:

const Nodemailer = require("nodemailer");
const { MailtrapTransport } = require("mailtrap");

const TOKEN = "<YOUR_API_TOKEN>";

const transport = Nodemailer.createTransport(
  MailtrapTransport({
    token: TOKEN,
  })
);

const sender = {
  address: "hello@demoatmailtrap.com",
  name: "Mailtrap Test",
};
const recipients = [
  "demo@mailtrap.io",
];

transport
  .sendMail({
    from: sender,
    to: recipients,
    subject: "You are awesome!",
    text: "Congrats for sending test email with Mailtrap!",
    category: "Integration Test",
  })
  .then(console.log, console.error);

The documentation is also quite extensive, regularly updated, and has everything you need in one place.

Additionally, Mailtrap has a blog with step-by-step articles on setting up the platform’s SMTP/API and sandbox with all major programming languages and web dev frameworks, such as:

On top of that, their YouTube team has been busy and provided a lot of follow-along videos on setting up sending or testing functionality, validation mechanisms, and more. Check it out.

Security 

From email authentication to detailed logs and monthly DKIM key rotation, Mailtrap has every security element covered:

Encryption & transmission securityStrong TLS enforcement, MTA-STS support
Authentication & identity controlSPF, DKIM, DMARC alignment
API & credentials securityGranular API keys, IP whitelisting
Account access & user controlsMFA, RBAC, detailed audit logs
Abuse prevention & misuse protectionRobust reputation management, real-time
security monitoring
Security event logging & notificationsDetailed logs, customizable alerts

Compliance

Mailtrap is compliant with all modern regulations, it’s ISO certified, and SOC 2 certification is in progress:

GDPR✅ Compliant
Data residency Based in EU but the servers are in the US
SOC 2, ISO 27001, HIPAA✅ 
User rights supportDSAR support & data deletion upon request
LoggingDetailed logs, exportable
DPA✅ Available on request

Testimonials

While scouring online reviews, I’ve noticed that Mailtrap is praised for its deliverability and dev-friendly API. One of the reviewers also mentioned how the Mailtrap support team helped them resolve DKIM alignment issues within a few hours:

Source: G2

Others like its API for its reliability and rapid delivery time:

Source: Capterra

Best for devs: Mailgun

G2: 4.2 🌟 Capterra: 4.3 🌟

Mailgun is a transactional email service that provides an SMTP and email API designed for developers. 

Here’s a quick breakdown of its most important features:

Dedicated IPsAvailable from 50k emails/month as an add-on and included from 100k emails/month.
Separate streams
Rate handling✅ Yes, limit not specified
Webhooks✅ Full events
Templates✅ Handlebars + versioning
Testing✅ Two separate products
Customer supportTicket, chat, and phone

Why is it the best for devs?

  • Webhook API

Mailgun’s webhook API can be supported at the domain level, which can be handy if you’re using multiple domains. Additionally, it supports many engagement events, such as accepted, delivered, spam complaints, and more.

If a webhook delivery fails, Mailgun will retry the delivery for up to 8 hours.

  • Email validation API

If you want to add email validation logic to your web forms, you can do so with Mailgun’s email validation API. Besides the basic syntax and DNS checks, Mailgun cross-references your email list against its database of 450 billion emails, and warns you about high-risk addresses.

You can also validate your contacts in bulk if you don’t feel like integrating.

  • Detailed email logs

Mailgun keeps your email logs for up to 30 days, but that’s not their biggest selling point. Namely, what makes them great is the fact that there are 10 filter fields you can use to customize your logs and then analyze them across all your domains.

These include TO and FROM headers, event types, list names, tag names, and others.

Source: Mailgun

Pricing

Mailgun has a generous free tier that lets you send 5,000 emails during the first month, which would make it perfect for startups if it didn’t lock away some important features like dedicated IPs to high-tier plans. Nonetheless, here’s a brief summary of its pricing:

PlanMonthly costEmail limitKey features
Free$0100 per dayEmail API and SMTP, 
1 custom sending domain,
2 API keys
1 day log retention
1 inbound route
BasicFrom $1510,000+Email API and SMTP, 
1 custom sending domain,
2 API keys
1 day log retention
FoundationFrom $3550,000+1,000 custom sending domains,
Email template builder and API,
5 days log retention,
ScaleFrom $90100,000+SAML SSO,
5,000 email validations,
Dedicated IP pools,
30 days log retention

For more details, please consult the official Mailgun pricing page.

Pros

  • High throughput
  • EU and US data centers
  • Rapid Fire Delivery SLA
  • Email validation
  • Onboarding support
  • Real-time tracking
  • Solid webhooks
  • Inbound email processing

Cons

  • The email testing suites are billed separately and can get pricey if you send high volumes of emails.
  • Only the highest-tier plan, Scale, offers 30 days of email logs.

Developer experience

Official API documentation

Mailgun supports Python, Go, Node.js, PHP, Java, and Ruby.

The email platform has a dedicated developer documentation page, which you can use to inspect any of its 4 APIs. The page layout is super clear, and navigating is a breeze, making it great even for junior developers. Night mode is also a big bonus.

The code snippets Mailgun provides aren’t as extensive as they come, but the platform has a nice blog where you can find some solutions to several programming languages. 

Security

Mailgun’s focus is on granular user permissions, has all encryption check boxes cleared, and is quite a secure API:

Encryption & transmission securityMandatory TLS, MTA-STS
Authentication & identity controlSPF, DKIM, DMARC
API & credentials securityManage API keys, IP restrictions
Account access & user controlsMFA, granular user permissions
Abuse prevention & misuse protectionSpam detection, bounce handling
Security event logging & notificationsDetailed event logs, webhooks for notifications

Compliance

Mailgun is compliant with GDPR, stores its data in the EU, and is compliant with all of the latest regulations. You can get more info on the compliance and security page or check out the summary table below:

GDPR✅ Compliant
Data residency EU region sending & storage
SOC 2, ISO 27001, HIPAA✅ 
User rights supportUser data deletion & subject access
LoggingLogging & audit trails
DPA✅ Available

Testimonials

Overall, although it has its issues, Mailgun has solid ratings on review websites. A reviewer that stood out to me praised Mailgun’s API and the email platform’s ability to help their company comply with inbox provider policies for Google, Microsoft, and Yahoo:

Source: G2

I also found a short case study, describing how a Ruby-based company, DNSimple, used HTTParty to integrate with Mailgun API, then programmatically created and configured domains, set up forwarding routes based on regex, and more.

Best for enterprises: SendGrid

G2: 4.0 🌟 Capterra: 4.2 🌟

SendGrid is one of the oldest names in the industry, providing an email API and SMTP service most suitable for enterprises due its high level of multitenancy support.

Although it doesn’t offer a separate sending stream, SendGrid’s API is overall flexible:

Dedicated IPsAvailable from 100k emails/month.
Separate streams
Rate handling✅ 10,000 r/s, 1,000 recipients/email
Webhooks✅ Full events + logs
Templates✅ Handlebars + versioning
Testing✅ Sandbox + features vary by plan
Customer supportTicket, chat, and phone

If you’re interested, check out how SendGrid compares to Mailtrap.

Why is it the best for enterprises?

  • Subuser accounts

If you own a multi-brand business, or an agency that has different clients, or if you simply need granular permission control, SendGrid lets you segment your sending and email API activity.

Namely, you can create subusers with specific permissions, give each user credit limits, etc. For example, you can set it up so that one user can only send transactional emails while another can send only bulk.

Most importantly, each subuser will have separate API credentials, stats, and sender reputation.

  • IP pool management

With SendGrid, you can assign dedicated IPs to different email types or group them together for better deliverability and sender reputation. 

Additionally, SendGrid offers IP Access Management, a strong security feature that lets you control who can access your account based on their IP address. 

  • Deliverability features

To help you ensure your emails land in main inboxes, SendGrid uses a cloud-based infrastructure and offers everything from warmed up geo-specific IPs to reputation monitoring and adaptive throttling and optimization.

You can also use SendGrid’s Deliverability Insights with its email API and webhooks to receive real-time notifications on key performance metrics.

Source: SendGrid

Pricing

SendGrid has straightforward pricing plans, although they can ramp up in cost if you intend to use the platform’s advanced features like dedicated IPs or have extra slots for teammates:

PlanMonthly costEmail limitKey features
EssentialsFrom $19.9550kAnalytics and deliverability insights,
Email API
Limited webhooks,
1 additional teammate
ProFrom $89.95100k All of the above
+Dedicated IPs, Validation API,
Reverse DNS,
1,000 additional teammates
PremierCustomCustomAll of the above + more

For more details, please consult the official SendGrid pricing page.

Pros

  • Pre-warmed up, geo-specific IPs
  • Quality of life features
  • Good documentation
  • Granular user control
  • Onboarding assistance
  • Long webhook retry windows
  • SMS support via Twilio
  • CRM support and integrations with other useful platforms

Cons

  • Dedicated IPs and reverse DNS are available only to high-tier users.
  • Slightly steeper learning curve since it’s geared towards developers.

Developer experience

Official API documentation

SendGrid supports C#, Go, Java, Node.js, PHP, Python, and Ruby.

The platform’s API documentation is pretty clear and has everything you need, although I especially liked the onboarding guide, which you can follow step-by-step when integrating the API.

There are also code snippets for everything, so your developers will have to spend minimal time coding.

The platform’s customer support team is also available via ticket, chat, and phone, although it’s locked to higher-tier plans.

Security

Besides offering detailed IP access management, SendGrid covers all security bases: 

Encryption & transmission securityEnforced TLS, MTA-STS
Authentication & identity controlSPF, DKIM, DMARC
API & credentials securityScoped API keys, IP access management
Account access & user controlsMFA, RBAC, SSO
Abuse prevention & misuse protectionReal-time spam feedback, proactive monitoring
Security event logging & notificationsActivity feed, email event webhooks

Compliance

With SendGrid, you can choose whether you want to send your emails from EU or US, which allows you to deliver them faster. Besides that, it’s compliant with all of the important regulations:

GDPR✅ Compliant
Data residency EU region selectable, US default
SOC 2, ISO 27001, HIPAA✅ 
User rights supportSupports DSARs, deletion, data export
Loggingvia Twilio’s security tools
DPA✅ Available

Testimonials

Although I’ve noticed people aren’t big fans of SendGrid’s customer support on social media and ratings websites, they seem to be pretty satisfied with the email sending service API. More specifically, with how easy it is to integrate it:

Source: G2

However, I’ve noticed the opposite on Capterra, so you be the judge:

Source: Capterra

Best for AWS users: Amazon SES

G2: 4.3 🌟Capterra: 4.7 🌟

Amazon SES, short for Simple Email Service, is a cloud-based email API provider that’s geared towards developer teams who are already using AWS and have technical expertise.

As for the flexibility aspect of Amazon SES, here’s a summary table:

Dedicated IPsAvailable as an add-on (paid); managed or bring-your-own IPs
Separate streams
Rate handling✅ Customizable sending quotas, throttling with SES sending limits
Webhooks✅ Uses Amazon SNS for event notifications (deliveries, bounces, complaints)
Templates✅ Supports dynamic templates via the SES API or SMTP
Testing✅ Sandbox mode for dev/testing environments; also supports test email domains
Customer support✅ Ticket, chat, phone, email

Why is it the best for AWS users?

  • AWS integration

As part of the AWS Global Infrastructure, Amazon SES can be integrated with various AWS services. Some of these include S3, Lambda, SNS Support, and others.

Although this can streamline a lot of workflows, I must mention that it requires technical expertise. 

  • Identity and access management

With AWS Identity and Access Management (IAM), you can fine-tune your permissions based on users, roles, or systems. This allows you to manage your API key authentication and management, separate access between clients or environments, and more.

Source: Amazon SES
  • CloudWatch monitoring

Another useful AWS integration is Amazon CloudWatch. By integrating Amazon SES with it, you can get metrics on email sends, bounces, spam complaints, rejects, and rendering failures.

You can also create custom dashboards to visualize your email delivery performance or even set alarms to get notified when a certain metric exceeds a threshold (e.g., when your bounce rate goes above 5%).

Source: Amazon SES

Pricing

Amazon SES has a super simple pricing model: you pay $0.10 per 1,000 emails, which equals $1 for 10,000 emails or $10 for 100,000 emails.

Moreover, if you’re using Amazon EC2 and AWS Elastic Beanstalk, you get the first 62,000 emails for free.

For more details, please consult the official Amazon SES pricing page.

Pros

  • Integration with AWS
  • Super configurable
  • Secure and compliant
  • Strong and reputable IPs
  • A/B testing
  • Solid webhooks support
  • Has servers in EU, US, and Asia
  • Scalable and affordable pricing model

Cons

  • Doesn’t have an in-built native analytics UI, so you need to integrate with a 3rd party service instead.
  • Requires coding experience and being comfortable with the AWS ecosystem to be used to its 100%.

Developer experience

Official API documentation

Amazon SES has official libraries for Java, .NET, PHP, Python, Ruby, and Go.

Although Amazon SES has robust documentation, I have to note that you also need a little bit of developer experience, as well as experience with the AWS ecosystem. This is especially true if you want to use the API to its fullest potential.

For example, using Amazon SES API to send emails requires you to verify your domain, move out of the SES sandbox mode since all accounts start in it, create IAM credentials, configure permissions, and only then install an AWS SDK and set up your credentials. See what I mean?

Security

Being a part of the Amazon Infrastructure, it’s safe to say that you don’t have to worry when it comes to Amazon SES and security:

Encryption & transmission securityOpportunistic / forced TLS, MTA-STS (manual setup)
Authentication & identity controlSPF, DKIM, custom MAIL FROM, DMARC
API & credentials securityIAM policies, granular access control
Account access & user controlsIAM, MFA, CloudTrail integration
Abuse prevention & misuse protectionReputation dashboards, feedback loops
Security event logging & notificationsExtensive logs via CloudWatch/
CloudTrail

Compliance

Similarly, Amazon SES covers all bases when it comes to compliance, even offering servers in Asia:

GDPR✅ Compliant
Data residency Region-specific data storage (EU/US/Asia)
SOC 2, ISO 27001, HIPAA✅ 
User rights supportIAM-level controls & data export tools
LoggingCloudTrail logging
DPA✅ Through AWS DPA

Testimonials

One of the most common remarks I’ve seen about Amazon SES is that it’s affordable:

Source: G2

I’ve also found many reviews that say Amazon SES is for developer teams experienced with AWS configurations, although they don’t like the fact that you need 3rd party integrations for analytics:

Source: Capterra

Best for transactional emails: Postmark

G2: 4.6 🌟 Capterra: 4.9 🌟

Postmark is an email platform that provides a transactional email API service for developers. 

It’s API is flexible, giving you room to play around with your infrastructure:

Dedicated IPsAvailable as an add-on from 300k emails/month
Separate streams✅ Transactional and broadcast
Rate handling✅ No limits, auto throttling
Webhooks✅ Standard events
Templates✅ Mustachio
Testing✅ Mustachio
Customer supportTicket

Why is it the best for transactional emails?

  • Separate sending streams

Postmark offers separate sending streams, similar to Mailtrap. The streams are dedicated to bulk emails (Broadcast Message Stream) and user-triggered emails (Transactional Message Stream).

Furthermore, you can create a custom stream for specific email types. So, for instance, you can create a separate stream for password reset emails, a separate one for invoices, etc.

  • Detailed event logs

With Postmark, you get to keep your email logs for up to 45 days, and they’re really detailed. 

You can filter the logs by status, subject, custom tags, and date. They’re also quite configurable. For example, you can configure them so you retrieve them automatically via Postmark’s Message API or even connect webhooks with them.

  • Transactional email templates

Welcome emails, receipts, invoices, user invitations, trial expirations; you name it. With Postmark Email Templates, you can create all kinds of designs for your app/project, and then send them when they’re ready via Postmark API.

The templates are powered by Mustachio, a lightweight templating engine that allows you to make dynamic email content

Source: Postmark

Pricing

Ever since its price increase in 2025, Postmark has been on the more expensive end, but nonetheless, it’s still more affordable than a lot of its competitors (looking at you, Mailchimp):

PlanMonthly costEmail limitKey features
Free$0100Email API,SMTP service,Core features likeemail templates, analytics, webhooks
BasicFrom $15,0010,000+Up to 4 users, SMTP & Rest API, Up to 5 servers and domains, Email templates
ProFrom $60,5050,000+Up to 6 users, Up to 30 streams, Up to 10 signature domains, All event webhooks, Stats & open/link,  tracking APIs
PlatformFrom $138,00125,000+Unlimited users, Unlimited servers, Unlimited streams, Unlimited signature domains, All event webhooks

For more details, please consult the official Postmark pricing page.

Pros

  • Straightforward setup
  • Separate sending streams
  • Fast email delivery
  • Transparent deliverability status
  • Inbound email support
  • Logs for up to 45 days
  • Real-time notifications with webhooks
  • Offers MCP agents 

Cons

  • You can reach Postmark customer support only via tickets and it’s not available 24/7.
  • To get dedicated IPs, you need to be sending at least 300,000 emails per month.

Developer experience

Jump to: Official API documentation

Postmark has official libraries for Ruby, RoR, .NET, Java, PHP, and Node.js.

The platform’s documentation is also very well organized, and it seems to be regularly updated. In translation: you don’t even need to be as experienced to use Postmark’s email API and start sending emails. 

Speaking of email sending, you get code snippets for every major programming language and web framework Postmark supports:

Security

The aspect I liked the most about Postmark’s security is the way it automatically blocks delivery for bounces and how detailed its activity logs are. It also has all important encryption protocols in place:

Encryption & transmission securityTLS 1.2+ enforced
Authentication & identity controlSPF, DKIM, DMARC
API & credentials securityRestricted API tokens, IP whitelisting.
Account access & user controlsMFA, team roles, activity feed
Abuse prevention & misuse protectionProactive spam filters, bounce management
Security event logging & notificationsDetailed activity logs, webhooks

Compliance

Besides allowing you to choose whether you want EU or US hosting, Postmark complies with key industry standards and certifications:

GDPR✅ Compliant
Data residency All data hosted in EU or US (choose)
SOC 2, ISO 27001, HIPAA✅ 
User rights supportData subject rights support
LoggingGranular activity logging
DPA✅ Available upon request

Testimonials

Generally, people like Postmark’s SMTP and API for sending transactional emails, although I’ve noticed that some have an issue with the platform’s customer support team not working around the clock and having only ticket support:

Source: G2

On the other hand, some people like the fact that Postmark supports whitelabel domains and has solid deliverability:

Source: Capterra

If you’re interested in exploring what Postmark users have to say about the platform and its API, you can also check out its customers page

Best for JS stack: Resend

G2: 4.3 🌟 Capterra: N/A

Launched in 2022, Resend is an email API provider with a focus on developer experience, simplicity, and tight integration with JavaScript frameworks.

Here’s how Resend performed on our email API flexibility tests:

Dedicated IPsAvailable as an add-on from 500 emails/day with auto warm-up.
Separate streams
Rate handling✅ No details on throttling
Webhooks✅ Limited, domain-focused
Templates❌ Manual
Testing❌ Test addresses only
Customer supportTicket and Slack

Why is it the best for dev teams who use JS stack?

  • React Email

React Email is an open-source framework by Resend that lets you build emails using React, the same way you would build UI components for web apps with JSX. To make it even more seamless, Resend offers different components and even email templates if you’re feeling stuck.

Of course, the platform offers its very own Node.js SDK, which means you can integrate easily and send your email templates via API whenever you think you’re ready to move to production.

  • Email templates

Not sure if your email designs are ready for production? Don’t worry, you can preview them with React Email and see how they look in React code, HTML, or plain text and on different devices like desktops and mobile phones.

Source: Resend
  • Vercel integration

If you have a Vercel project, you can integrate it with Resend directly through the dashboard in a few clicks and automatically create a new API key linked to your domain. This will instantly add it as an environment variable in your Vercel project, saving you time and the hassle of managing multiple dependencies.

You can also use the Resend template, which provides you with a pre-configured Next.js project integrated with a React Email template. This allows you to send transactional emails right away with minimal coding efforts.

Source: Resend

Pricing

Resend is deemed one of the most affordable API providers out there, with generous sending limits and an abundance of features equally spread throughout the 4 plans it offers. Check them out:

PlanMonthly costEmail limitKey features
Free$03,000Restful API, SMTP relay, 1 day data retention, 1 domain, 100 emails a day
ProFrom $2050,0003-day data retention, 10 domains, no daily sending limit, 10 webhook endpoints
ScaleFrom $90100,000Slack & ticket support, 7-day data retention, 1,000 domains, dedicated IP with add-on
EnterpriseCustomCustomAll of the above

For more details, please consult the official Resend pricing page.

Pros

  • Minimal UI 
  • Developer-friendly email service
  • Lightweight Node.js SDK
  • Suppression management
  • Maintained GitHub repos
  • Solid customer support
  • Integration with TypeScript
  • Supports attachments via API
  • Generous free plan

Cons

  • Email logs are kept only for up to 7 days on all tiers except Enterprise.
  • Lacks advanced analytics and insights on deliverability metrics.

Developer experience

Jump to: Official API documentation

Resend supports Node.js, PHP, Laravel, Python, Ruby, Go, Java, Rust, and .NET.

Besides the minimalistic UI and user-friendly design, Resend offers comprehensive documentation. In its super in-depth knowledge base, you can find everything from DNS guides to deliverability troubleshooting guides. 

What I liked the most is that you get detailed logs with request headers and response body, through which you can analyze your API traffic, calls, and more.

Source: Resend

Resend also offers many code snippets for integrating their API, which you can simply copy/paste into your configuration to start sending. For instance, here’s the script they provide for Node.js: 

import { Resend } from 'resend';
const resend = new Resend('re_xxxxxxxxx');
await resend.emails.send({  from: 'Acme <onboarding@resend.dev>',  to: ['delivered@resend.dev'],  subject: 'hello world',  html: '<p>it works!</p>',});

Security

Resend has a transparent security page, where I was able, among other pages, to find a lot of information for this review: 

Encryption & transmission securityTLS encryption, MTA-STS support
Authentication & identity controlSPF, DKIM, DMARC alignment
API & credentials securityAPI tokens with scope-based access, environment separation (Prod/Sandbox)
Account access & user controlsTeam-based roles, organization-level access control
Abuse prevention & misuse protectionDedicated IPs (on request), domain-level reputation tracking
Security event logging & notificationsActivity logs in dashboard, email alerts for failures

Compliance

As of now, Resend doesn’t support HIPAA, hasn’t started pursuing ISO certification, but it’s SOC compliant. Other than that, it’s flexible when it comes to data residency and is quite complaint:

GDPR✅ Compliant
Data residency EU or US (you choose during domain setup)
SOC 2, ISO 27001, HIPAASOC 2 compliant; HIPAA not officially supported, not ISO-certified
User rights support✅ Data subject rights support (e.g., access and deletion requests)
Logging✅ Detailed activity logs, API-level request tracking, and webhooks
DPA✅ Available upon request
GDPR✅ Already addressed above

Testimonials

Because it’s a relatively new platform, I wasn’t able to find many Resend reviews. However, the ones I did find tell a story. For example, the first one that grabbed my attention talks about Resend’s API first approach, React Email integration, its strong deliverability features, and more. 

Source: G2

There’s more praise for Resend’s API, its documentation, and good analytics:

Source: G2

Transactional email API comparison criteria

To select the best email API on the market, I used the following criteria:

Email infrastructure

When talking about email infrastructure, we are actually talking about the following aspects:

Deliverability

Email APIs with high deliverability rates are more likely to send your emails to your recipients’ inboxes, instead of delivering them to the spam folder. 

However, as the exact rates are not publicly available, we’ve run a few deliverability tests for some of the providers on the list. And yes, the tests were fair for all email API providers: we made sure to use a free plan, shared IP, the same template, and no domain warmup. 

Here are the results (other providers’ results are on the way):

Email service providerEmail placement result
MailtrapInbox: 78.8%
Tabs: 4.8%
Spam: 14.4%
Missing: 2.0%
Amazon SESInbox: 77.1%
Tabs: 1.9%
Spam: 20.0%
Missing: 1.0%
MailgunInbox: 71.4%
Tabs: 3.8%
Spam: 23.8%
Missing: 1.0%
SendGridInbox: 61.0%
Tabs: 1.0%
Spam: 17.1%
Missing: 20.9%
PostmarkInbox: 83.3%
Tabs: 1.0%
Spam: 14.3%
Missing: 0.9%

For the full results and insights into the methodology we used, check out our dedicated blog post on email deliverability comparison.

Scalability & throughput handling

As far as reliability goes, an ideal email API is one with the least amount of downtime and always-ready customer support. So, I’ve scoured the web looking for downtime reports and checked out each API’s customer support availability.

To take it one step further, I’ve checked out various status pages like this one or delivery pages like this one.

Reliability & uptime

As your business grows, the email API you use will have to adapt to your growing needs and handle different email-sending volumes without compromising the quality of the service.

And although not all services on this list provide good scalability, you can send large amounts of emails with all of them.

IP pools & email streams

A solid IP infrastructure consists of features such as dedicated IPs, manual or auto warm-up, IP pool management, etc. 

I’ll also look into separate sending streams, which go a long way when it comes to deliverability since they allow you to send transactional and marketing emails on separate IPs. 

Now, some API providers offer dedicated infrastructures through IP pooling or email queuing, but a true separate stream is what you need if you’re a high-volume email sender. That is, if you don’t want your emails to hit spam filters or damage your sender reputation.

Pricing comparison

An email API should be affordable, but at the same time, not cut back on important features like email logs or dedicated IP addresses. It should offer value for money and also let you choose a pricing plan according to the size of your business. For now, check out what you can expect from each provider’s pricing plans:

SMTP provider10,000 emails50,000 emails100,000 emails250,000 emails
Mailtrap$15$20$30$200
Mailgun$15$35$75$215
SendGrid$19.95$35$60$200
Amazon SES$1,00$5,00$10,00$25,00
Postmark$15$50$100$250

Ease of integration

Most providers nowadays support simple mail transfer protocol (SMTP), allowing you to send emails via relay mechanisms over RESTful API endpoints. To help you integrate the API with your project, they also offer SDKs, toolkits that contain everything from installation instructions to pre-built components and resources.

So, for research purposes of this article, I’ll dive head first into the documentation, GitHub repositories, and SDKs of every email service I review. I’ll check which programming languages they’re compatible with, the usage examples they offer, and more!

I’ll also look for quality-of-life features, which aren’t necessary at all, but can make your developer team’s lives easier. A great example is MCP servers, such as Mailtrap MCP and Postmark MCP. You can hook these up to your IDE or preferred AI helper, then test your transactional emails or smooth out your workflow.

Webhooks

With webhooks, you can get instant notifications when your emails get delivered or land in spam, when someone unsubscribes, etc. You can monitor your engagement, debug workflows, you name it.

Since all email API providers on this list offer webhooks, I’ll compare them by the types of events they support and their retry logic. 

Testing environment

Email testing is an inseparable part of a rock-solid email-sending cycle, as you don’t want your recipients to receive faulty messages. Moreover, integrating an email API with your app/project often comes with writing a lot of code.

So, I’ll be sure to look out for any testing features the email APIs I’ve come across offer.

Email analytics

Detailed analytics on email performance, such as open rates, bounce rates, and click-through rates, go a long way in improving your deliverability.

This is especially true since all major inbox providers nowadays have their own regulations, including:

To comply with these, you need to be able to track your emails. For instance, Google requires you to stay under 0.1% spam rate if you don’t want to get blocked.

However, it’s important to make a distinction in the analytics email API providers offer. Some provide dedicated solutions like Mailtrap, while others, like Amazon SES, require integration with other services such as CloudWatch.

Security & compliance

Security 

Every email API should place strong emphasis on encrypting data, requiring authentication, and similar security measures. 

For the purposes of this article, I’ve researched how each provider handles encryption, API keys, how granular their user access is, if they support TLS and STARTTLS protocols, etc.

P.S. Over at Mailtrap, we’ve recently conducted in-depth research on email security for the top providers in the industry. Check it out! 

Compliance

Not complying with regulations like GDPR (EU) or CCPA (US), CAN-SPAM Act, and others can lead to considerable fines. For instance, not complying with the CAN-SPAM Act, you can get fined up to $44k per email.

So, to see whether an email API provider helps you comply with all the regulations, I’ve dug through pages like this one or this one.

Since the Mailtrap team leaves no stone unturned, we’ve also compared the compliance of the top providers. You can read it here.

Onboarding, UX & support

HTML previews, blacklist checks, email logs, webhook responses in JSON format, and templates are only some of the features every email API should offer to cater to diverse use cases and enhance user experience.

Additionally, verifying your domain shouldn’t be a headache, and a blocker shouldn’t take forever to deal with. That’s why I’ve checked what sort of customer support the API providers from this list offer and whether:

  • Their team is available around the clock or not
  • You get help if you’re migrating from another provider
  • They provide email deliverability consultations

Customer experience

I’ll make sure to provide you with user testimonials for each platform I’ve found across the various social media platforms.

And I’ll also dig out the ratings from popular review websites such as G2 or Capterra.

Wrapping up

And we’ve made it!

I hope you enjoyed going through the haystack of email infrastructure services and best email APIs with me and that I’ve made your decision on which one to use a bit easier.

And as if you haven’t had enough of tables throughout this article, here’s another one that sums up the best email APIs for you:

Email APIBest forIntegrationPricing
MailtrapHigh-volume product companiesNode.js, PHP, Ruby, Python, Elixir, JavaFrom $15
MailgunDeveloper teamsPython, Go, Node.js, PHP, Java, RubyFrom $15
SendGridEnterprise usersC#, Go, Java, Node.js, PHP, Python, RubyFrom $19.95
Amazon SESAWS users and devsJava, .NET, PHP, Python, Ruby, Go$0.10 per 1,000 emails
PostmarkTransactional emailsRuby, RoR, .NET, Java, PHP, Node.jsFrom $15
ResendJS stack usersNode.js, PHP, Laravel, Python, Ruby, Go, Java, Rust, .NETFrom $20

P.S. In case you’re a high-volume sender, make sure to check out the video our awesome YouTube team has prepared for you. ⬇️

Frequently asked questions

What is the best email API?

Since every team has its specific goals, needs, and wants, there really is no best email API. However, Mailtrap Email API is quite flexible and lets you control your sending process and fine-tune it according to your requirements. 

Which email API offers the best deliverability rates?

Based on the deliverability tests we’ve recently performed, Mailtrap and Postmark have the best deliverability rates. Using free plans, shared IPs, and identical email template, we’ve managed to achieve 78.8% deliverability rate with Mailtrap, whereas Postmark reached 83.3%.

How do I choose the best email API for my application?

When choosing the best email API for your application, first take into consideration your team’s requirements and goals. Then, take into account an API’s email infrastructure, ease of integration, webhooks, testing environment, email analytics, security & compliance, and, of course, customer support and pricing.

If you need help choosing an email API, refer to our guide on choosing an email service provider.  

Ivan Djuric, an author at Mailtrap
Article by Ivan Djuric Technical Content Writer @Mailtrap

I’m a Technical Content Writer with 5 years of background covering email-related topics in tight collaboration with software engineers and email marketers. I just love to research and share actionable insights with you about email sending, testing, deliverability improvements, and more. Happy to be your guide in the world of emails!