5 Best Email API For Developers Compared [2026]

With so many email API providers out there, picking the right one can be tough. You have to sort through documentation, compare prices, and decide which features are important for your needs.

We’ve compared five popular providers for you: AgentMail, Resend, SendGrid, Mailgun, and Amazon SES. This guide looks at sending, receiving and pricing for large volumes, and new use cases like AI agents.

By the end, you’ll know which provider fits your tech stack best.

How We Evaluated

We assessed each API across six dimensions:

1. Sending capabilities: SMTP, REST API, SDK support
2. Receiving capabilities: Full inbox vs. webhook-only vs. none
3. Deliverability: SPF, DKIM, DMARC handling
4. Developer experience: Documentation, SDKs, error messages
5. Pricing: Free tier, scaling costs, transparency
6. Specialized features: AI integrations, semantic search, templates

Each provider is strong in different areas, so the best choice depends on what you need.

Let’s take a closer look at each provider.

1. AgentMail — Best for AI Agents

Website: agentmail.to

AgentMail is an email API designed for AI agents and automated workflows. Unlike traditional email APIs, AgentMail offers a full inbox setup, including programmatic inbox creation, sending, receiving, threading, parsing, filtering, labeling, and storage.

It works natively with any AI framework, including popular options like LangChain, LlamaIndex, and CrewAI.

Key Features

• Programmatic Inbox Creation: Create inboxes via API: no manual setup, no admin consoles.
• Two-Way Email: Send and receive capabilities with persistent message storage.
• Email Threading: Built-in threading via API with comprehensive Message-ID, In-Reply-To, and References email headers
• Metadata Labeling: String-based labels for organizing, categorizing, managing, and querying the state of your conversations.
• Intelligent Parsing: Automatic extraction of structured data from HTML and attachments.
• Event-driven architecture: Configurable webhooks and WebSockets for real-time email events
• Framework Integrations: Native support for LangChain, LlamaIndex, and CrewAI.

Developer Experience

AgentMail puts developer experience first, especially for teams working on AI agents and automation.

• SDKs and Language Support

  AgentMail offers official SDKs for Python and Node.js, with full TypeScript support. Both SDKs follow the API structure closely, making it easy to switch between languages. The Python SDK also integrates smoothly with AI frameworks like LangChain, LlamaIndex, and CrewAI.

• Authentication

  Authentication is simple: just use an API key. There’s no need for OAuth, token refresh, or complex permissions. You generate a key in the dashboard and can start right away. This is helpful for AI agents that need to work on their own without manual steps.

• Documentation

  AgentMail’s documentation is thorough, with code examples for every endpoint in both Python and Node.js. It covers common workflows from creating an inbox to sending emails and listing replies. There are also guides for AI-specific tasks, like setting up webhooks for agent notifications.

• Time to First Email

  You can go from signup to sending your first email in under three minutes. The onboarding process guides you through creating an inbox and sending a test message. You don’t need to verify your domain to start, but it’s recommended for production use.

• Multitenant support

  AgentMail offers a unique feature called “pods.” A pod groups inboxes and domains for a single customer, user, or agent. Everything in a pod is kept separate, so email data doesn’t mix with other pods. This makes it easy to run multi-tenant systems, giving each customer or agent their own email workspace.

• Error Handling

  AgentMail provides clear error messages with helpful suggestions. Instead of a generic “400 Bad Request,” you’ll see specific feedback like “inbox_id not found” or “domain not verified for sending.” Rate limit errors also tell you when to try again.

Here’s a quick integration video showing AgentMail in action:

Code Example

Creating an inbox, sending an email, and listing received messages:

from agentmail import AgentMail

client = AgentMail(api_key="your_api_key")

# Create an inbox programmatically
inbox = client.inboxes.create(
    username="support-agent",
    domain="yourdomain.com"
)

# Send an email
client.messages.send(
    inbox_id=inbox.id,
    to="customer@example.com",
    subject="Your order has shipped",
    body="Tracking number: ABC123..."
)

# List received emails
messages = client.messages.list(inbox_id=inbox.id)
for msg in messages:
    print(f"From: {msg.sender}, Subject: {msg.subject}")

Pricing

Source: agentmail.to/pricing

Strengths

• Complete inbox infrastructure, not just sending.
• Programmatic inbox creation at scale
• AI-native features like semantic search
• Usage-based scaling
• Native AI framework integrations

Ideal For

• AI agent developers building autonomous systems
• Automation workflows requiring send + receive
• Applications needing programmatic inbox management
• Testing pipelines requiring isolated inboxes

2. Resend

Website: resend.com

Resend is a newer email API provider that started in 2023. It offers a simple API for sending transactional emails. The company also built React Email, an open-source library for creating emails with React components.

Key Features

• React Email Integration: Build emails using React components.
• Clean API Design: Straightforward endpoints with minimal configuration.
• Regional Sending: Choose between US and EU data centers.
• Webhooks: Real-time notifications for email events.
• Inbound Email: Receive emails via webhooks (added in 2025).

Developer Experience

• SDKs and Language Support

  Resend has official SDKs for Node.js, Python, Ruby, Go, Elixir, and PHP. The Node.js SDK is the most developed, since Resend focuses on the React ecosystem. The other SDKs handle the basics but might not have the latest features right away.

• Authentication

  Authentication uses a single API key and is easy to set up. However, lower pricing tiers don’t include scoped permissions or team-based access controls.

• Documentation

  The documentation is clear and focused, helping you get started quickly. The API reference includes examples for every endpoint. Resend also keeps separate docs for React Email templates.

• Time to First Email

  Setup is quick, and you can send your first email just minutes after signing up. You’ll need to verify your domain for production use.

• Error Messages

  Error responses are clear and concise, using standard HTTP status codes and JSON error messages.

Code Example

Sending a transactional email:

import { Resend } from 'resend';

const resend = new Resend('re_123456789');

await resend.emails.send({
  from: 'onboarding@yourdomain.com',
  to: 'user@example.com',
  subject: 'Welcome!',
  html: '<p>Thanks for signing up!</p>'
});

Pricing

Source: resend.com/pricing

Strengths

• Excellent developer experience
• React Email for component-based templates.
• Generous free tier
• Clean, modern documentation
• Inbound email support via webhooks

Considerations

• Inbound email works through webhooks, not a persistent inbox. If you need storage and threading, you may want to look at other providers.
• Fewer enterprise features than SendGrid

Ideal For

• React and Next.js developers
• Primarily sending use cases where receiving is secondary

3. SendGrid

Website: sendgrid.com

SendGrid has been around since 2009 and was acquired by Twilio in 2019. It supports both transactional and marketing emails, making it a popular choice for companies that want both in one platform.

SendGrid is built to handle large volumes. For receiving emails, it uses Inbound Parse, which sends a webhook to your endpoint but doesn’t offer persistent storage or threading.

Key Features

• SMTP and REST API: Multiple integration options.
• Marketing Campaigns: Built-in tools for email marketing.
• Advanced Analytics: Deliverability insights, engagement metrics.
• Inbound Parse: Receive emails via webhook (stateless).
• IP Warm-up: Automated reputation building.
• Subuser Management: Granular permissions for teams.

Developer Experience

• SDKs

  Official libraries for C#, Go, Java, Node.js, PHP, Python, and Ruby. The SDKs are mature and well-maintained, reflecting over a decade of iteration.

• Authentication

  API key-based authentication. SendGrid supports scoped API keys, which let you limit permissions for different keys. Two-factor authentication is available for account access.

• Documentation

  The documentation covers all features, but it can feel scattered. Some sections are outdated, and switching between old and new APIs can be confusing. However, the knowledge base is large and helpful for troubleshooting.

• Time to First Email

  It usually takes 10 to 15 minutes to send your first email, since there are more setup steps than with newer providers. You’ll need to verify your sender and authenticate your domain for production.

• Error Messages

  SendGrid gives detailed error responses with specific codes. Sometimes, you’ll need to check the documentation to figure out the cause and how to fix it.

Code Example

Sending an email using the Python SDK:

from sendgrid import SendGridAPIClient
from sendgrid.helpers.mail import Mail

sg = SendGridAPIClient(api_key='SG.xxx')

message = Mail(
    from_email='sender@example.com',
    to_emails='recipient@example.com',
    subject='Hello from SendGrid',
    html_content='<p>Email content here</p>'
)

response = sg.send(message)
print(response.status_code)

Pricing

Source: sendgrid.com/pricing

Strengths

• Comprehensive feature set
• Strong documentation and SDKs
• Twilio ecosystem integration
• Dedicated IP options

Considerations

• Inbound Parse is stateless, so there’s no persistent inbox or threading. If you need conversation history for AI agents or automation, you’ll want a provider with a full inbox setup.
• Pricing can be complex with add-ons.
• Some users report variable support quality (Source: Trustpilot)

Ideal For

• Enterprise companies with high-volume needs
• Organizations needing both marketing and transactional email
• Teams already using Twilio services
• Primarily outbound use cases

4. Mailgun

Website: mailgun.com

Mailgun was founded in 2010 and acquired by Sinch in 2021. It’s aimed at developers who want detailed control over their email setup, offering in-depth logging, flexible routing, and a built-in email validation API.

Mailgun lets you send and receive emails, but inbound processing uses webhooks and doesn’t include persistent storage. Many developers choose Mailgun for its routing engine, which supports complex rules for handling incoming messages.

Key Features

• Email Validation API: Verify email addresses before sending.
• Detailed Logs: Track every email event with configurable retention.
• Routing Rules: Complex logic for handling inbound email.
• Inbound Routing: Receive emails via webhook.
• Multiple SDKs: Python, Go, Node.js, PHP, Java, Ruby.

Developer Experience

• SDKs

  Official libraries for Python, Go, Node.js, PHP, Java, and Ruby. The SDKs wrap the REST API and handle authentication, retries, and response parsing. The Python SDK is particularly popular and well-maintained. You can use the REST API directly with any HTTP client, which many developers prefer for simpler integrations.

• Authentication

  API key via HTTP Basic Auth. Your API key serves as the password with “api” as the username. This approach works with any HTTP library without needing a dedicated SDK. Mailgun also supports domain-specific API keys, so you can isolate credentials per sending domain.

• Documentation

  Well-documented with code examples in multiple programming languages. The API reference covers all endpoints with request/response samples. Some sections reference older patterns, but the core documentation is reliable. Mailgun also provides guides for everyday use cases, such as transactional emails, inbound routing, and email validation.

• Time to First Email

  Expect 10-15 minutes to send your first email. Domain verification is mandatory, which involves adding DNS records (SPF, DKIM, and MX for receiving). Mailgun provides a sandbox domain for testing, so you can send to authorized recipients immediately while setting up your production domain.

• Error Messages

  Clear error responses with specific codes and messages. The API returns JSON containing a message field that explains what went wrong. Rate limit errors include headers indicating when you can retry. Validation errors identify the problematic field, making debugging straightforward.

Code Example

Sending an email using the REST API:

import requests

response = requests.post(
    "https://api.mailgun.net/v3/YOUR_DOMAIN/messages",
    auth=("api", "YOUR_API_KEY"),
    data={
        "from": "sender@yourdomain.com",
        "to": "recipient@example.com",
        "subject": "Hello from Mailgun",
        "text": "Email content here"
    }
)

Pricing

Source: mailgun.com/pricing

Strengths

• Email validation API included
• Flexible routing and rules engine
• Strong deliverability track record
• Detailed event logs
• Good documentation

Considerations

• Inbound email is a webhook posted to your endpoint.
• Pricing increased in recent years.
• Log retention varies by plan.
• Some users report slower response times from support.

Ideal For

• Teams needing email validation
• Complex routing requirements
• Developers wanting granular control over email infrastructure
• Use cases where validation is as important as delivery

5. Amazon SES

Website: aws.amazon.com/ses

Amazon Simple Email Service (SES) launched in 2011 as part of the AWS ecosystem. It handles email sending and receiving at scale, integrating directly with other AWS services like S3, Lambda, and SNS.

The platform operates on a pay-as-you-go model with some of the lowest per-email costs in the industry. However, receiving email requires additional AWS infrastructure setup, and there is no persistent inbox or threading built in.

Key Features

• SMTP and API: Send via REST API or SMTP relay.
• Email Receiving: Process incoming emails via receipt rules.
• AWS Integration: Store emails in S3, trigger Lambda functions, publish to SNS.
• Virtual Deliverability Manager: Insights and recommendations for email performance.
• Reputation Dashboard: Track bounce and complaint rates.
• Configuration Sets: Group sending settings and track metrics per set.

Developer Experience

• SDKs

  AWS offers SDKs for Python (Boto3), JavaScript, Java, .NET, Go, Ruby, PHP, and more. These SDKs are part of the larger AWS ecosystem, so if you already use AWS, the patterns will be familiar. They handle authentication, retries, and errors in a consistent way across all AWS services.

• Authentication

  SES uses IAM-based authentication with AWS access keys or IAM roles. This is more complex than using a simple API key, but it gives you detailed control over permissions. You can limit access to certain SES actions with IAM policies. For apps on EC2 or Lambda, IAM roles mean you don’t have to manage credentials yourself.

• Documentation

  The documentation is thorough but spread across several AWS sites. The SES Developer Guide explains concepts and setup, while SDK docs are separate. This can be overwhelming if you’re new to AWS. There are also code examples in the SDK docs and on GitHub.

• Time to First Email

  If you’re new to AWS, setup takes about 30 to 60 minutes. New accounts start in sandbox mode, so you can only send to verified addresses. To go live, you need to request approval from AWS, which can take 24 to 48 hours. You’ll also need to set up DNS records for domain verification (DKIM, SPF). If you already use AWS, setup is faster because IAM handles authentication.

• Error Messages

  SES returns standard AWS error codes and messages. The SDK shows exceptions with specific error types, like MessageRejected or ConfigurationSetDoesNotExist. CloudWatch integration gives you detailed logs and metrics to help troubleshoot deliverability problems.

Code Example

Sending an email using the AWS SDK for Python (Boto3):

import boto3

client = boto3.client('ses', region_name='us-east-1')

response = client.send_email(
    Source='sender@yourdomain.com',
    Destination={
        'ToAddresses': ['recipient@example.com']
    },
    Message={
        'Subject': {'Data': 'Hello from Amazon SES'},
        'Body': {
            'Text': {'Data': 'Email content here'},
            'Html': {'Data': '<p>Email content here</p>'}
        }
    }
)
print(response['MessageId'])

Pricing

Source: aws.amazon.com/ses/pricing

Strengths

• Lowest cost per email at scale
• Deep AWS system integration
• Highly reliable infrastructure
• Flexible receiving with Lambda triggers
• No monthly minimums

Considerations

• Sandbox mode limits new accounts until they are approved.
• Setup is more complex than standalone email APIs
• Receiving requires additional AWS infrastructure (S3, Lambda, SNS)
• SES doesn’t have a persistent inbox or threading. If your AI agents need conversation history and semantic search, AgentMail offers a full inbox setup without AWS’s added complexity.
• IAM learning curve for teams new to AWS

Ideal For

• Teams already using AWS infrastructure
• High-volume senders seeking cost-effectiveness
• Applications needing Lambda-triggered email processing
• Developers comfortable with AWS patterns

Picking the Right Email API

The best email API for you depends on what you’re building. Here’s how to approach the decision.

First, ask yourself: Do you need to receive email?

If you just need to send transactional emails like password resets, receipts, or notifications, most providers here will work. Choose based on developer experience and pricing.

If you need to receive and process incoming emails, your choices are more limited. SendGrid, Resend, Mailgun, and Amazon SES let you receive emails through webhooks, but you’ll have to handle storage, threading, and search yourself. AgentMail, on the other hand, provides a full inbox setup with storage, automatic threading, and semantic search built in.

Choose the provider that best fits your architecture.

AgentMail: Building AI agents, automation workflows, or anything that needs programmatic inbox creation and two-way email. You want email infrastructure to be API-first and out of the box for everything, including storage, threading, parsing, and search, so that you can focus on your application logic.

Resend: Developer experience matters most. You’re building with modern frameworks (React, Next.js) and want a clean API with minimal friction. Sending is your primary use case.

SendGrid: Enterprise scale with proven reliability. You need both marketing and transactional email in one platform, or you’re already in the Twilio ecosystem and want unified billing.

Mailgun: Granular control over email infrastructure. You need email validation, complex routing rules, or detailed logs. You prefer flexibility and don’t mind more configuration.

Amazon SES: You're running on AWS and want the lowest cost per email. You're comfortable with IAM, Lambda, and managing your own storage with S3. Setup complexity is acceptable for the cost savings.

What really sets providers apart

It comes down to what you need: Can you receive emails? Search past messages? Create inboxes with code? Keep conversations threaded for automation?

If your app uses email just for notifications, most providers here will do the job. But if email is central to your product, customer support, AI agents, or workflow automation, you’ll need infrastructure that covers the entire email lifecycle.