SMTP Servers - Documentation

Quick Start

Get started with SMTP Servers in just a few minutes. Our service provides a reliable SMTP relay that you can integrate with any application that sends email.

Step 1: Create an Account

Sign up for a free account at smtp-servers.com/signup. After registration, verify your email address to activate your account.

Step 2: Get Your Credentials

Once logged in, navigate to your Customer Dashboard

To find your SMTP credentials. You'll need:

SMTP Server: relay.smtp-servers.com
Port: 2525
Username: Your SMTP Username
Password: Your SMTP password

Step 3: Send Your First Email

Configure your application with the credentials above and send a test email:

Node.js

const nodemailer = require('nodemailer');

const transporter = nodemailer.createTransport({
  host: 'relay.smtp-servers.com',
  port: 2525,
  secure: false,
  auth: {
    user: 'your SMTP username',
    pass: 'your SMTP password'
  }
});

await transporter.sendMail({
  from: 'sender@yourdomain.com',
  to: 'recipient@example.com',
  subject: 'Hello from SMTP Servers!',
  text: 'This is my first email.'
});

Tip: Use port 2525 for the best compatibility with firewalls and email clients.

Authentication

SMTP Servers uses standard SMTP authentication. We support both PLAIN and LOGIN authentication mechanisms.

Credentials

Field	Value	Description
`Username`	Your SMTP Credential (username)	This is the username created in SMTP Credential page
`Password`	Your SMTP password	This is the password created in SMTP Credential page

Security: Never expose your SMTP credentials in client-side code or public repositories. Use environment variables to store sensitive information.

SMTP Settings

Use the following settings to configure your email client or application:

Setting	Value
SMTP Server	`relay.smtp-servers.com`
Port	`2525`
Authentication	Required (PLAIN or LOGIN)
Encryption	TLS/SSL Required

Node.js Integration

Use Nodemailer, the most popular email sending library for Node.js.

Installation

bash

npm install nodemailer

Send Email

JavaScript

const nodemailer = require('nodemailer');

// Create transporter
const transporter = nodemailer.createTransport({
  host: process.env.SMTP_HOST || 'relay.smtp-servers.com',
  port: process.env.SMTP_PORT || 2525,
  secure: false, // true for 465, false for 2525
  auth: {
    user: process.env.SMTP_USER,
    pass: process.env.SMTP_PASS
  }
});

// Send email
async function sendEmail() {
  try {
    const info = await transporter.sendMail({
      from: '"Your Name" <sender@yourdomain.com>',
      to: 'recipient@example.com',
      subject: 'Test Email',
      text: 'Plain text content',
      html: '<p>HTML content</p>'
    });
    console.log('Email sent:', info.messageId);
  } catch (error) {
    console.error('Error:', error);
  }
}

sendEmail();

Python Integration

Python's built-in smtplib makes it easy to send emails.

Python

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

# Configuration
SMTP_HOST = os.environ.get('SMTP_HOST', 'relay.smtp-servers.com')
SMTP_PORT = 2525
SMTP_USER = os.environ.get('SMTP_USER')
SMTP_PASS = os.environ.get('SMTP_PASS')

# Create message
msg = MIMEMultipart('alternative')
msg['Subject'] = 'Test Email'
msg['From'] = 'sender@yourdomain.com'
msg['To'] = 'recipient@example.com'

text = 'Plain text content'
html = '<p>HTML content</p>'

msg.attach(MIMEText(text, 'plain'))
msg.attach(MIMEText(html, 'html'))

# Send email
with smtplib.SMTP(SMTP_HOST, SMTP_PORT) as server:
    server.starttls()
    server.login(SMTP_USER, SMTP_PASS)
    server.send_message(msg)
    print('Email sent successfully!')

PHP Integration

We recommend using PHPMailer for sending emails in PHP.

Installation

bash

composer require phpmailer/phpmailer

Send Email

PHP

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

require 'vendor/autoload.php';

$mail = new PHPMailer(true);

try {
    // Server settings
    $mail->isSMTP();
    $mail->Host       = 'relay.smtp-servers.com';
    $mail->SMTPAuth   = true;
    $mail->Username   = getenv('SMTP_USER');
    $mail->Password   = getenv('SMTP_PASS');
    $mail->SMTPSecure = PHPMailer::ENCRYPTION_STARTTLS;
    $mail->Port       = 2525;

    // Recipients
    $mail->setFrom('sender@yourdomain.com', 'Your Name');
    $mail->addAddress('recipient@example.com');

    // Content
    $mail->isHTML(true);
    $mail->Subject = 'Test Email';
    $mail->Body    = '<p>HTML content</p>';
    $mail->AltBody = 'Plain text content';

    $mail->send();
    echo 'Email sent successfully!';
} catch (Exception $e) {
    echo "Error: {$mail->ErrorInfo}";
}
?>

Java Integration

Use Jakarta Mail (formerly JavaMail) for sending emails in Java applications.

Java

import jakarta.mail.*;
import jakarta.mail.internet.*;
import java.util.Properties;

public class EmailSender {
    public static void main(String[] args) {
        String host = "relay.smtp-servers.com";
        String username = System.getenv("SMTP_USER");
        String password = System.getenv("SMTP_PASS");

        Properties props = new Properties();
        props.put("mail.smtp.auth", "true");
        props.put("mail.smtp.starttls.enable", "true");
        props.put("mail.smtp.host", host);
        props.put("mail.smtp.port", "2525");

        Session session = Session.getInstance(props,
            new Authenticator() {
                protected PasswordAuthentication getPasswordAuthentication() {
                    return new PasswordAuthentication(username, password);
                }
            });

        try {
            Message message = new MimeMessage(session);
            message.setFrom(new InternetAddress("sender@yourdomain.com"));
            message.setRecipients(Message.RecipientType.TO,
                InternetAddress.parse("recipient@example.com"));
            message.setSubject("Test Email");
            message.setText("Hello from SMTP Servers!");

            Transport.send(message);
            System.out.println("Email sent successfully!");
        } catch (MessagingException e) {
            e.printStackTrace();
        }
    }
}

cURL / Raw SMTP

Test your connection using cURL or telnet for debugging purposes.

bash

# Test SMTP connection with cURL
curl --url 'smtp://relay.smtp-servers.com:2525' \
  --ssl-reqd \
  --mail-from 'sender@yourdomain.com' \
  --mail-rcpt 'recipient@example.com' \
  --user 'your-email@example.com:your-password' \
  --upload-file email.txt

Rate Limits

Rate limits depend on your subscription plan:

Plan	Daily Limit	Monthly Limit	Rate (per minute)
Starter	1,000	10,000	60
Professional	5,000	50,000	300
Business	20,000	200,000	1,000
Enterprise	Custom	Custom	Custom

Note: If you exceed your rate limit, emails will be queued and sent when capacity becomes available.

Error Handling

Always implement proper error handling in your email sending code.

JavaScript

async function sendEmailWithRetry(mailOptions, maxRetries = 3) {
  for (let attempt = 1; attempt <= maxRetries; attempt++) {
    try {
      const result = await transporter.sendMail(mailOptions);
      return result;
    } catch (error) {
      console.error(`Attempt ${attempt} failed:`, error.message);

      if (attempt === maxRetries) {
        throw error;
      }

      // Wait before retrying (exponential backoff)
      await new Promise(r => setTimeout(r, 1000 * attempt));
    }
  }
}

Best Practices

1. Use Environment Variables

Never hardcode credentials in your source code. Use environment variables instead.

2. Implement Retry Logic

Network issues can cause temporary failures. Implement exponential backoff for retries.

3. Validate Email Addresses

Validate recipient email addresses before sending to reduce bounce rates.

4. Use Proper From Address

Use a from address from a domain you own and have properly configured with SPF/DKIM records.

5. Monitor Your Sending

Regularly check your dashboard for delivery rates, bounces, and complaints.

Pro Tip: Set up a dedicated subdomain for transactional emails (e.g., mail.yourdomain.com) to protect your main domain's reputation.

SMTP Response Codes

Common SMTP response codes you may encounter:

Code	Meaning	Action
`250`	Success	Email accepted for delivery
`421`	Service unavailable	Retry later
`450`	Mailbox unavailable	Retry later
`451`	Local error	Retry later
`452`	Insufficient storage	Retry later
`500`	Syntax error	Check your request
`535`	Authentication failed	Check credentials
`550`	Mailbox not found	Verify recipient address
`552`	Message too large	Reduce message size

Troubleshooting

Connection Timeout

If you're experiencing connection timeouts, ensure port 2525 or 465 is not blocked by your firewall. Some hosting providers block outbound SMTP connections.

Authentication Failed

Double-check your username and password. Ensure you're using your registered email as the username. If you recently changed your password, make sure to update it in your application.

Emails Not Delivering

Check your dashboard for any error messages or bounces. Verify that your sender domain has proper DNS records (SPF, DKIM, DMARC) configured.

Rate Limit Exceeded

If you're hitting rate limits, consider upgrading your plan or implementing queuing in your application to spread out email sending over time.

Need Help? Contact our support team at support or check your dashboard for detailed logs and error messages.