Adapters

Adapters

Supported email service adapters and transports.

Email SDK ships with 17 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.

Resend

Popular APIs

OfficialPayload-testedLive account required

@opencoredev/email-sdk/resend

Postmark

Popular APIs

OfficialPayload-testedLive account required

@opencoredev/email-sdk/postmark

SendGrid

Popular APIs

OfficialPayload-testedLive account required

@opencoredev/email-sdk/sendgrid

AWS SES

Infrastructure

OfficialPayload-testedLive account required

@opencoredev/email-sdk/ses

Mailgun

Popular APIs

OfficialPayload-testedLive account required

@opencoredev/email-sdk/mailgun

MailerSend

Popular APIs

OfficialPayload-testedLive account required

@opencoredev/email-sdk/mailersend

Brevo

Popular APIs

OfficialPayload-testedLive account required

@opencoredev/email-sdk/brevo

Mailchimp Transactional

Popular APIs

OfficialPayload-testedLive account required

@opencoredev/email-sdk/mailchimp

SparkPost

Infrastructure

OfficialPayload-testedLive account required

@opencoredev/email-sdk/sparkpost

Mailtrap

Infrastructure

OfficialPayload-testedLive account required

@opencoredev/email-sdk/mailtrap

Cloudflare Email Sending

Infrastructure

OfficialPayload-testedLive account required

@opencoredev/email-sdk/cloudflare

Scaleway

Infrastructure

OfficialPayload-testedLive account required

@opencoredev/email-sdk/scaleway

ZeptoMail

Infrastructure

OfficialPayload-testedLive account required

@opencoredev/email-sdk/zeptomail

MailPace

Infrastructure

OfficialPayload-testedLive account required

@opencoredev/email-sdk/mailpace

Loops

Product-led

OfficialPayload-testedLive account required

@opencoredev/email-sdk/loops

Plunk

Product-led

OfficialPayload-testedLive account required

@opencoredev/email-sdk/plunk

SMTP

SMTP

Transport

OfficialBuilt-in transportSMTP server required

@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, or Brevo
A backup route for production delivery	A primary API adapter plus Postmark or SMTP
Product-triggered emails	Loops or Plunk
A cheap or self-managed transport	SMTP
Heavy attachment support	Resend, Postmark, SendGrid, Mailgun, MailerSend, Mailtrap

What the status labels mean

Provider cards use three labels:

Official means the adapter ships in @opencoredev/email-sdk.
Payload-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.
Live account required means final delivery still depends on provider setup: verified domains, sender identities, API scopes, sandbox settings, regions, rate limits, and provider policy.
SMTP server required means final delivery depends on the SMTP host, credentials, and TLS settings you provide.

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

Import pattern

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"],
});

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	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?What the status labels mean Import pattern Adapter groups