# Email Service > Email sending patterns for transactional and marketing emails. Use when implementing email sending, templates, SMTP configuration, or email services like SendGrid, Resend, or Mailgun. - Skill: `majiayu000/email-service-3` (Agent Skill, multi-file: 2 files) - Install (CLI): `npx skillmds@latest add majiayu000/email-service-3` - Raw SKILL.md: https://api.skillmd.com/api/skills/majiayu000/email-service-3/raw - Safety review: pending (external: skill-scanner PASS, skillspector PASS) - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: Marketing & Growth - Author: majiayu000 (https://skillmd.com/u/majiayu000) - Updated: 2026-09-09 - Page: https://skillmd.com/skills/majiayu000/email-service-3 --- # Email Service Patterns ## Setup (Resend — recommended) ```python # email.py import resend resend.api_key = settings.RESEND_API_KEY async def send_email( to: str | list[str], subject: str, html: str, from_email: str = "noreply@yourdomain.com", ) -> str: """Send transactional email, return message ID.""" params = resend.Emails.SendParams( from_=from_email, to=[to] if isinstance(to, str) else to, subject=subject, html=html, ) email = resend.Emails.send(params) return email["id"] ``` ```typescript // lib/email.ts import { Resend } from 'resend' const resend = new Resend(process.env.RESEND_API_KEY) export async function sendEmail(params: { to: string | string[] subject: string html: string from?: string }) { const { data, error } = await resend.emails.send({ from: params.from ?? 'noreply@yourdomain.com', to: Array.isArray(params.to) ? params.to : [params.to], subject: params.subject, html: params.html, }) if (error) throw new Error(error.message) return data } ``` ## Setup (SendGrid) ```python from sendgrid import SendGridAPIClient from sendgrid.helpers.mail import Mail def send_email_sendgrid(to: str, subject: str, html: str): message = Mail( from_email="noreply@yourdomain.com", to_emails=to, subject=subject, html_content=html, ) client = SendGridAPIClient(settings.SENDGRID_API_KEY) response = client.send(message) return response.status_code ``` ## HTML Email Templates (React Email) ```tsx // emails/WelcomeEmail.tsx import { Html, Head, Body, Container, Text, Button, Hr } from '@react-email/components' interface WelcomeEmailProps { username: string verifyUrl: string } export function WelcomeEmail({ username, verifyUrl }: WelcomeEmailProps) { return ( Welcome, {username}! 👋 Thanks for signing up. Please verify your email address to get started.

If you didn't create an account, you can safely ignore this email. ) } // Render to HTML for sending import { render } from '@react-email/render' const html = render() ``` ## Common Email Types ```python # email_service.py from .templates import render_template async def send_welcome_email(user_email: str, username: str, verify_token: str): verify_url = f"{BASE_URL}/verify?token={verify_token}" html = render_template("welcome.html", username=username, verify_url=verify_url) await send_email(user_email, f"Welcome to MyApp, {username}!", html) async def send_password_reset(email: str, reset_token: str): reset_url = f"{BASE_URL}/reset-password?token={reset_token}" html = render_template("password_reset.html", reset_url=reset_url) await send_email(email, "Reset your password", html) async def send_invoice(email: str, invoice_data: dict): html = render_template("invoice.html", **invoice_data) await send_email(email, f"Invoice #{invoice_data['invoice_number']}", html) async def send_notification(email: str, title: str, message: str): html = f"""

{title}

{message}

""" await send_email(email, title, html) ``` ## Jinja2 Templates (Python) ```python from jinja2 import Environment, FileSystemLoader env = Environment(loader=FileSystemLoader("templates/emails")) def render_template(template_name: str, **context) -> str: template = env.get_template(template_name) return template.render(**context) ``` ```html

Welcome, {{ username }}! 👋

Click below to verify your email:

Verify Email

This link expires in 24 hours.

``` ## Email Queue (Background with Celery) ```python from celery import Celery celery = Celery("tasks", broker=settings.REDIS_URL) @celery.task(bind=True, max_retries=3, default_retry_delay=60) def send_email_task(self, to: str, subject: str, html: str): try: send_email_sync(to, subject, html) except Exception as exc: raise self.retry(exc=exc) # Usage — don't block the request send_email_task.delay(user.email, "Welcome!", welcome_html) ``` ## SMTP (nodemailer / standard SMTP) ```typescript import nodemailer from 'nodemailer' const transporter = nodemailer.createTransport({ host: process.env.SMTP_HOST, port: 587, secure: false, auth: { user: process.env.SMTP_USER, pass: process.env.SMTP_PASS, }, }) export async function sendEmail(to: string, subject: string, html: string) { await transporter.sendMail({ from: '"MyApp" ', to, subject, html, }) } ``` ## Rules - Use a transactional email service (Resend, SendGrid, Mailgun) — NEVER raw SMTP in production - Always queue emails (Celery/background task) — never send synchronously in request handler - Verify sender domain with SPF, DKIM, DMARC records (deliverability) - Never build HTML emails with `f-strings` with user input (XSS in email clients) - Include unsubscribe link in marketing emails (CAN-SPAM / GDPR) - Test email rendering with Litmus or Email on Acid before launch - Rate limit: max 1 email per minute per recipient to avoid spam classification - Use separate API keys for transactional vs marketing emails - Log email send attempts (ID, recipient, template, status) in your DB