Sending Emails via SMTP | Cakemail Documentation

Send emails through Cakemail's SMTP gateway using standard SMTP protocol. This allows you to leverage the full power of Cakemail's Email API without modifying your existing SMTP-based applications.

Overview

The SMTP gateway provides a familiar interface for developers already using SMTP. Simply configure your SMTP client to use Cakemail's server with your account credentials.

Benefits:

Use existing SMTP libraries and code
Minimal changes to legacy applications
Standard protocol with wide language support
Industry-leading deliverability

Email API Subscription Required

Before using SMTP, you need an active Email API account with a valid subscription.

Learn more at cakemail.com/solutions/email-api.

SMTP Configuration

Setting	Value
Host	`smtp.cakemail.dev`
Port	`465`
Encryption	SSL/TLS (SMTPS)
Authentication	Your Cakemail username and password

Prerequisites

Sender Requirements

Your sender address must be:

Registered in your Cakemail account
Validated through email verification
Authenticated with SPF/DKIM records
Tracking domain branded on your domain

The From: header must match a validated sender. Emails from unvalidated senders will be rejected.

List ID

Contact management is required for compliance and bounce handling. You'll need a List ID from your Cakemail account. Find your default list or create a new one through the Lists API.

Required Headers

x-email-api-enabled

Format: x-email-api-enabled: true

Enables Email API routing for this message. Required for all SMTP messages.

x-list-id

Format: x-list-id: <list-id>

Associates the email with a Cakemail list. Required by default.

Why x-list-id is required:

Consent management: Maintains compliance with email regulations
Bounce handling: Automatically processes bounces and unsubscribes
Contact management: Recipients not in the list are automatically added

If your use case justifies not using a list ID, contact support@cakemail.com.

Optional Headers

Header	Format	Default	Purpose
`x-email-api-type`	`marketing` or `transactional`	`marketing`	Email type classification
`x-tags`	`tag1,tag2`	None	Comma-separated tags for filtering

Quick Start

curl -v \
    --mail-from 'sender@example.com' \
    --mail-rcpt 'recipient@example.com' \
    smtps://smtp.cakemail.dev:465 \
    --user "your-username:your-password" \
    --upload-file - <<EOF
From: sender@example.com
To: recipient@example.com
Subject: Test Email
x-email-api-enabled: true
x-list-id: 9234980

This is the email body content.
EOF

Code Examples

Python (smtplib)

import smtplib
from email.mime.text import MIMEText
from email.mime.multipart import MIMEMultipart

smtp_server = "smtp.cakemail.dev"
smtp_port = 465
username = "your-username"
password = "your-password"

msg = MIMEMultipart()
msg['From'] = 'sender@example.com'
msg['To'] = 'recipient@example.com'
msg['Subject'] = 'Test Email'
msg['x-email-api-enabled'] = 'true'
msg['x-list-id'] = '9234980'

body = "This is the email body content."
msg.attach(MIMEText(body, 'plain'))

with smtplib.SMTP_SSL(smtp_server, smtp_port) as server:
    server.login(username, password)
    server.send_message(msg)
    print("Email sent successfully!")

Node.js (nodemailer)

const nodemailer = require('nodemailer');

const transporter = nodemailer.createTransport({
  host: 'smtp.cakemail.dev',
  port: 465,
  secure: true,
  auth: {
    user: 'your-username',
    pass: 'your-password'
  }
});

const mailOptions = {
  from: 'sender@example.com',
  to: 'recipient@example.com',
  subject: 'Test Email',
  text: 'This is the email body content.',
  headers: {
    'x-email-api-enabled': 'true',
    'x-list-id': '9234980'
  }
};

transporter.sendMail(mailOptions, (error, info) => {
  if (error) {
    console.error('Error:', error);
  } else {
    console.log('Email sent:', info.response);
  }
});

PHP (PHPMailer)

<?php
use PHPMailer\PHPMailer\PHPMailer;
use PHPMailer\PHPMailer\Exception;

require 'vendor/autoload.php';

$mail = new PHPMailer(true);

try {
    $mail->isSMTP();
    $mail->Host       = 'smtp.cakemail.dev';
    $mail->SMTPAuth   = true;
    $mail->Username   = 'your-username';
    $mail->Password   = 'your-password';
    $mail->SMTPSecure = PHPMailer::ENCRYPTION_SMTPS;
    $mail->Port       = 465;

    $mail->setFrom('sender@example.com');
    $mail->addAddress('recipient@example.com');

    $mail->addCustomHeader('x-email-api-enabled', 'true');
    $mail->addCustomHeader('x-list-id', '9234980');

    $mail->Subject = 'Test Email';
    $mail->Body    = 'This is the email body content.';

    $mail->send();
    echo 'Email sent successfully!';
} catch (Exception $e) {
    echo "Email could not be sent. Error: {$mail->ErrorInfo}";
}

Troubleshooting

Authentication Failed

Verify your Cakemail username and password
Ensure your account has API access enabled

Connection Refused

Confirm you're using port 465 with SSL/TLS
Check if your firewall allows outbound connections on port 465
Verify the hostname is smtp.cakemail.dev

Email Not Delivered

Ensure x-email-api-enabled: true header is included
Confirm the sender email is validated and authenticated
Check that x-list-id contains a valid list ID
Review spam/junk folders

Limitations

Single recipient per SMTP call — send separately for multiple recipients
Attachments disabled by default — contact support@cakemail.com to enable