Adapters

Adapters

Supported email service adapters and transports.

Email SDK ships with 20 adapters. Import only the adapter you use; the package does not ask you to configure providers that are not on your send path.

Every adapter follows the same contract: map the fields it supports and throw a validation error for fields the provider API cannot represent. Use the SDK field support guide before choosing fallback routes.

Sponsors

Companies helping keep Email SDK practical and maintained. Open slots are available.

Special sponsors

SponsorSequenzy Open slotSponsor Open slotSponsor Open slotSponsor

Resend

Popular APIs

OfficialNot API testedRequest tested

@opencoredev/email-sdk/resend

Postmark

Popular APIs

OfficialNot API testedRequest tested

@opencoredev/email-sdk/postmark

SendGrid

Popular APIs

OfficialNot API testedRequest tested

@opencoredev/email-sdk/sendgrid

AWS SES

Infrastructure

OfficialNot API testedRequest tested

@opencoredev/email-sdk/ses

Mailgun

Popular APIs

OfficialNot API testedRequest tested

@opencoredev/email-sdk/mailgun

MailerSend

Popular APIs

OfficialNot API testedRequest tested

@opencoredev/email-sdk/mailersend

Brevo

Popular APIs

OfficialNot API testedRequest tested

@opencoredev/email-sdk/brevo

Mailchimp Transactional

Popular APIs

OfficialNot API testedRequest tested

@opencoredev/email-sdk/mailchimp

SparkPost

Infrastructure

OfficialNot API testedRequest tested

@opencoredev/email-sdk/sparkpost

Mailtrap

Infrastructure

OfficialNot API testedRequest tested

@opencoredev/email-sdk/mailtrap

Cloudflare Email Sending

Infrastructure

OfficialNot API testedRequest tested

@opencoredev/email-sdk/cloudflare

Scaleway

Infrastructure

OfficialNot API testedRequest tested

@opencoredev/email-sdk/scaleway

ZeptoMail

Infrastructure

OfficialNot API testedRequest tested

@opencoredev/email-sdk/zeptomail

MailPace

Infrastructure

OfficialNot API testedRequest tested

@opencoredev/email-sdk/mailpace

Loops

Product-led

OfficialNot API testedRequest tested

@opencoredev/email-sdk/loops

Plunk

Product-led

OfficialNot API testedRequest tested

@opencoredev/email-sdk/plunk

SMTP

SMTP

Transport

OfficialNo provider APIBuilt-in transport

@opencoredev/email-sdk/smtp

Which adapter should I start with?

If you want...	Start with
The fastest first send	Resend
Mature transactional delivery controls	Postmark, SendGrid, AWS SES, Mailgun, Unosend, or Brevo
A backup route for production delivery	A primary API adapter plus Postmark or SMTP
Product-triggered emails	Iterable, Sequenzy, Loops, or Plunk
A cheap or self-managed transport	SMTP
Heavy attachment support	Resend, Postmark, SendGrid, Mailgun, Unosend, MailerSend, Mailtrap, Sequenzy

Want to build a community adapter?

Do not add third-party provider experiments to the official package by default. Publish a separate community package, export an adapter plugin, and list it in the community registry if you want discoverability.

Create an adapter

Implement the provider mapping and wrap it as an adapter plugin.

Publish a community adapter

Build and publish a third-party provider package without making it official.

What the status labels mean

Provider cards use these labels:

Official means the adapter ships in @opencoredev/email-sdk.
Sponsor means the provider supports Email SDK. Sponsor adapters appear first in the catalog.
API tested means a local check has successfully called a live provider API with a real key. It does not prove live delivery unless the adapter page says a send was performed.
Not API tested means we have not yet run a live provider API check for that adapter.
Request tested means repository tests cover request mapping, responses, and fail-fast validation with injected fetch calls.
Built-in transport means the adapter sends through Email SDK's own transport implementation instead of a provider API.
No provider API means the adapter does not call a hosted provider API.

Email SDK can catch unsupported fields before a request. It cannot make a provider account ready to send from an unverified domain.

Import pattern

Start with one adapter. Add a fallback only after the fallback supports the same message shape your app sends.

import { createEmailClient } from "@opencoredev/email-sdk";
import { resend } from "@opencoredev/email-sdk/resend";
import { smtp } from "@opencoredev/email-sdk/smtp";

const email = createEmailClient({
  adapters: [
    resend({ apiKey: process.env.RESEND_API_KEY! }),
    smtp({
      host: process.env.SMTP_HOST!,
      auth: {
        user: process.env.SMTP_USER!,
        pass: process.env.SMTP_PASS!,
      },
    }),
  ],
  fallback: ["smtp"],
});

Route a single send through another configured adapter when a message has a provider-specific job.

const response = await email.send(
  {
    from: "Acme <hello@acme.com>",
    to: "user@example.com",
    subject: "Password reset",
    text: "Use this link to reset your password.",
  },
  {
    adapter: "smtp",
  },
);

console.log(response.provider);

Before adding the provider to production, run a dry run and then a live smoke test from the same environment that will send mail.

npx email-sdk adapters
RESEND_API_KEY="re_..." npx email-sdk send \
  --dry-run \
  --adapter resend \
  --from "Acme <hello@acme.com>" \
  --to user@example.com \
  --subject "Dry run" \
  --text "Validate only"

Adapter groups

Group	Adapters
Popular APIs	Resend, Postmark, SendGrid, Mailgun, MailerSend, Brevo, Mailchimp Transactional
Infrastructure	Cloudflare Email Sending, SparkPost, Mailtrap, Scaleway, ZeptoMail, MailPace
Product-led	Iterable, Sequenzy, Loops, Plunk
Transport	Built-in SMTP

Hooks

Observe sends without changing adapter code.

SDK field support

See which EmailMessage fields Email SDK maps for each adapter.

On this page

Which adapter should I start with?Want to build a community adapter?What the status labels mean Import pattern Adapter groups