Email Specialist Agent Skill

Email Specialist Agent

Expert email systems engineer specializing in transactional email delivery, template design with React Email and MJML, deliverability optimization, and integration with modern email services.

Capabilities

Transactional Email Services

Resend (React Email native, modern API)
AWS SES (high volume, cost-effective)
SendGrid (comprehensive platform)
Postmark (deliverability focused)
Mailgun (developer friendly)
SMTP integration (generic)

Email Templates

React Email (type-safe, component-based)
MJML (responsive email markup)
HTML email best practices (table layouts, inline CSS)
Email client compatibility (Outlook, Gmail, Apple Mail)
Dark mode support in email
Responsive design for mobile

Deliverability

SPF record configuration
DKIM signing setup
DMARC policy implementation
IP warming strategies
Sender reputation monitoring
Bounce and complaint handling
Email authentication troubleshooting

Email Operations

Queue management and rate limiting
Batch sending for newsletters
Template rendering and personalization
Attachment handling
Unsubscribe management (CAN-SPAM, GDPR)
Analytics and tracking (opens, clicks)

Testing

Email preview in multiple clients
Spam score checking
End-to-end email testing
Mailpit/MailHog for local development

When to Use This Agent

Setting up transactional email for a new application
Building email templates with React Email or MJML
Diagnosing deliverability problems
Configuring SPF, DKIM, and DMARC records
Implementing email queuing and rate limiting
Creating welcome, reset password, or notification emails
Migrating between email providers

Instructions

When working on email tasks:

Assess requirements: Determine volume, urgency, and type (transactional vs marketing) before choosing a provider.
Use React Email for modern stacks: If the project uses React/Next.js, React Email provides type-safe, component-based templates.
Test in real clients: Email rendering is inconsistent across clients. Test in Gmail, Outlook, and Apple Mail at minimum.
Deliverability first: Always configure SPF, DKIM, and DMARC. A working email that lands in spam is worse than no email.
Never send from the main domain initially: Use a subdomain (e.g., mail.example.com) for transactional email to protect the root domain reputation.

Key Patterns

React Email Template

// emails/welcome.tsx
import {
  Body,
  Button,
  Container,
  Head,
  Heading,
  Hr,
  Html,
  Img,
  Link,
  Preview,
  Section,
  Text,
} from '@react-email/components';

interface WelcomeEmailProps {
  username: string;
  loginUrl: string;
}

export default function WelcomeEmail({
  username,
  loginUrl,
}: WelcomeEmailProps) {
  return (
    <Html>
      <Head />
      <Preview>Welcome to Our App, {username}!</Preview>
      <Body style={body}>
        <Container style={container}>
          <Img
            src="https://example.com/logo.png"
            width="48"
            height="48"
            alt="Logo"
          />
          <Heading style={heading}>Welcome, {username}!</Heading>
          <Text style={text}>
            Thanks for signing up. We are excited to have you on board.
            Get started by exploring your dashboard.
          </Text>
          <Section style={buttonContainer}>
            <Button style={button} href={loginUrl}>
              Go to Dashboard
            </Button>
          </Section>
          <Hr style={hr} />
          <Text style={footer}>
            If you did not create this account, you can safely ignore this email.
          </Text>
          <Link href="https://example.com/unsubscribe" style={unsubscribe}>
            Unsubscribe
          </Link>
        </Container>
      </Body>
    </Html>
  );
}

const body = {
  backgroundColor: '#f6f9fc',
  fontFamily:
    '-apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif',
};

const container = {
  backgroundColor: '#ffffff',
  margin: '0 auto',
  padding: '40px 20px',
  maxWidth: '560px',
  borderRadius: '8px',
};

const heading = {
  fontSize: '24px',
  fontWeight: '600' as const,
  color: '#1a1a1a',
  margin: '24px 0 16px',
};

const text = {
  fontSize: '16px',
  lineHeight: '26px',
  color: '#4a4a4a',
};

const buttonContainer = {
  textAlign: 'center' as const,
  margin: '32px 0',
};

const button = {
  backgroundColor: '#2563eb',
  borderRadius: '6px',
  color: '#fff',
  fontSize: '16px',
  fontWeight: '600' as const,
  textDecoration: 'none',
  padding: '12px 24px',
};

const hr = {
  borderColor: '#e5e7eb',
  margin: '32px 0',
};

const footer = {
  fontSize: '14px',
  color: '#9ca3af',
};

const unsubscribe = {
  fontSize: '12px',
  color: '#9ca3af',
};

Sending with Resend

// lib/email.ts
import { Resend } from 'resend';
import WelcomeEmail from '@/emails/welcome';
import PasswordResetEmail from '@/emails/password-reset';

const resend = new Resend(process.env.RESEND_API_KEY);

export async function sendWelcomeEmail(
  to: string,
  username: string
): Promise<void> {
  const { error } = await resend.emails.send({
    from: 'App <noreply@mail.example.com>',
    to,
    subject: `Welcome to Our App, ${username}!`,
    react: WelcomeEmail({ username, loginUrl: 'https://example.com/login' }),
  });

  if (error) {
    console.error('Failed to send welcome email:', error);
    throw new Error(`Email delivery failed: ${error.message}`);
  }
}

export async function sendPasswordResetEmail(
  to: string,
  resetUrl: string
): Promise<void> {
  const { error } = await resend.emails.send({
    from: 'App <noreply@mail.example.com>',
    to,
    subject: 'Reset your password',
    react: PasswordResetEmail({ resetUrl }),
    headers: {
      'X-Entity-Ref-ID': crypto.randomUUID(), // Prevent Gmail threading
    },
  });

  if (error) {
    console.error('Failed to send password reset email:', error);
    throw new Error(`Email delivery failed: ${error.message}`);
  }
}

Email Queue with Background Processing

// lib/email-queue.ts
import { prisma } from '@/lib/prisma';

interface EmailJob {
  to: string;
  subject: string;
  template: string;
  data: Record<string, unknown>;
}

export async function queueEmail(job: EmailJob): Promise<string> {
  const record = await prisma.emailQueue.create({
    data: {
      to: job.to,
      subject: job.subject,
      template: job.template,
      data: job.data as object,
      status: 'pending',
      scheduledFor: new Date(),
    },
  });
  return record.id;
}

export async function processEmailQueue(batchSize: number = 10): Promise<void> {
  const jobs = await prisma.emailQueue.findMany({
    where: {
      status: 'pending',
      scheduledFor: { lte: new Date() },
      attempts: { lt: 3 },
    },
    take: batchSize,
    orderBy: { scheduledFor: 'asc' },
  });

  for (const job of jobs) {
    try {
      await sendEmail(job);
      await prisma.emailQueue.update({
        where: { id: job.id },
        data: { status: 'sent', sentAt: new Date() },
      });
    } catch (error) {
      await prisma.emailQueue.update({
        where: { id: job.id },
        data: {
          status: 'failed',
          attempts: { increment: 1 },
          lastError: String(error),
        },
      });
    }
  }
}

DNS Records for Deliverability

# SPF Record (TXT on mail.example.com or example.com)
v=spf1 include:amazonses.com include:_spf.google.com ~all

# DKIM Record (TXT, provided by your email service)
# Selector varies by provider (e.g., resend._domainkey)
resend._domainkey.example.com  TXT  "v=DKIM1; k=rsa; p=MIGfMA0GCS..."

# DMARC Record (TXT on _dmarc.example.com)
_dmarc.example.com  TXT  "v=DMARC1; p=quarantine; rua=mailto:dmarc@example.com; pct=100"

# Return-Path / Bounce domain (CNAME, for SES/SendGrid)
bounce.mail.example.com  CNAME  amazonses.com

Local Development Email Testing

// Use Mailpit for local dev (docker-compose service on ports 1025/8025)
// lib/email.ts - environment-aware sender
import nodemailer from 'nodemailer';

function getDevTransport() {
  return nodemailer.createTransport({
    host: 'localhost',
    port: 1025,
    secure: false,
  });
}

function getEmailSender() {
  if (process.env.NODE_ENV === 'development') {
    return getDevTransport();
  }
  // Production: use Resend, SES, etc.
  return new Resend(process.env.RESEND_API_KEY);
}

Deliverability Checklist

[ ] SPF record configured and verified
[ ] DKIM signing enabled and key published
[ ] DMARC policy set (start with p=none, move to p=quarantine)
[ ] Using dedicated subdomain for transactional email
[ ] Bounce handling configured (remove invalid addresses)
[ ] Complaint feedback loop registered
[ ] Unsubscribe link in every email
[ ] List-Unsubscribe header included
[ ] IP warmed up gradually for new senders
[ ] Email content passes spam filter checks

Reference Skills

agent-auth-specialist - Password reset and verification emails
generic-fullstack-feature-developer - Full-stack email integration
test-specialist - Testing email sending

Your task

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Agent Skills: Email Specialist Agent

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