How to Send Email Using SMTP Relay? Best Tips

To send email using SMTP relay, you configure your application, website, or email client to route outgoing emails through a trusted SMTP server instead of sending them directly from your own server. This SMTP relay server authenticates your request, applies security checks, and delivers your emails to the recipient’s mail server with better reliability, higher deliverability, and lower risk of spam blocking.

Step-by-Step: How to Send Email Using SMTP Relay

Step 1: Choose an SMTP Relay Provider

You can use:

• Gmail SMTP

• Outlook SMTP

• Amazon SES

• SendGrid

• Mailgun

• Your own VPS SMTP server (Postfix, Exim)

For beginners, a third-party relay is strongly recommended.

Step 2: Gather SMTP Details

You’ll need:

• SMTP host (example: smtp.example.com)

• SMTP port (587 or 465)

• Username

• Password

• Encryption type (TLS/SSL)

Step 3: Configure Your Application or Website

Below is a generic SMTP configuration example:

This configuration works for:

• WordPress

• PHP mailers

• Python apps

• Node.js

• CRM tools

• Marketing platforms

Step 4: Add Email Authentication (Very Important)

Without authentication, your emails will likely land in spam.

SPF Record

Allows the SMTP relay to send emails on behalf of your domain.

Example:

DKIM Record

Adds a cryptographic signature proving email authenticity.

Provided by your SMTP relay provider.

DMARC Record

Tells receiving servers how to handle unauthenticated emails.

Example:

Sending Email Using SMTP Relay in Popular Platforms

WordPress

Use plugins like:

• WP Mail SMTP

• FluentSMTP

• Post SMTP Mailer

Just enter your SMTP details and test email delivery.

PHP Example (PHPMailer)

Python Example

Common SMTP Relay Errors and Fixes

“Connection refused”

• Port blocked by hosting provider

• Try port 587 or 2525

“Authentication failed”

• Wrong username/password

• SMTP auth disabled

Emails going to spam

• Missing SPF/DKIM/DMARC

• Poor email content

• New sending domain with no reputation

SMTP Relay vs Direct Mail Sending

SMTP relay clearly wins in real-world usage.

Best Practices for SMTP Relay

• Always use authenticated SMTP

• Warm up new domains slowly

• Avoid spam-trigger words

• Use consistent “From” addresses

• Monitor bounce and complaint rates

• Enable TLS encryption

• Rotate credentials periodically

Is SMTP Relay Secure?

Yes—when configured correctly.

SMTP relay supports:

• TLS/SSL encryption

• Authentication

• IP whitelisting

• Activity logging

• Abuse prevention

It’s far more secure than sending emails directly from unmanaged servers.

Now let’s break this down properly—step by step—so you understand what SMTP relay is, why it matters, and exactly how to use it.

What Is SMTP Relay?

SMTP stands for Simple Mail Transfer Protocol, the standard protocol used to send emails across the internet.
An SMTP relay is a mail server that accepts outgoing emails from another server or application and forwards (relays) them to the recipient’s email server.

Instead of sending emails directly from your web server or app (which often causes delivery failures), you send them through a relay server that is already trusted by email providers like Gmail, Outlook, and Yahoo.

In simple terms:

• Your app → SMTP relay → recipient inbox

Why Use an SMTP Relay?

Using an SMTP relay is not optional anymore—it’s essential if you want emails to land in inboxes instead of spam folders.

Key benefits of SMTP relay

1. Higher deliverability
   SMTP relay providers maintain strong IP reputations, which improves inbox placement.

2. Authentication support
   Relays support SPF, DKIM, and DMARC—critical for passing spam filters.

3. Scalability
   You can send thousands or millions of emails without overwhelming your server.

4. Security
   Emails are sent using encrypted connections (TLS/SSL).

5. Reliability
   If one mail server is unavailable, relays retry delivery automatically.

Common Use Cases for SMTP Relay

SMTP relay is widely used in:

• Website contact forms

• Transactional emails (password reset, order confirmation)

• Bulk marketing emails

• Application notifications

• SaaS platforms

• CRM systems

• WordPress sites

• VPS or dedicated servers without mail setup

How SMTP Relay Works (Behind the Scenes)

Here’s what happens when you send an email using SMTP relay:

1. Your app or server connects to the SMTP relay server

2. It authenticates using a username/password or IP authorization

3. The email is submitted to the relay

4. The relay checks spam rules and email authentication

5. The relay forwards the email to the recipient’s mail server

6. The recipient server delivers the email to the inbox (or spam folder)

SMTP Relay Requirements

Before sending email via SMTP relay, you need:

• An SMTP relay provider or mail server

• SMTP credentials (host, port, username, password)

• A verified sending domain

• Proper DNS records (SPF, DKIM, DMARC)

• An email-sending application or client

Common SMTP Relay Ports

Port 587 is the industry standard and safest choice.

Final Thoughts

Sending email using SMTP relay is the most reliable, secure, and professional way to deliver emails from websites, applications, and servers. Whether you’re running a small blog or a high-volume SaaS platform, SMTP relay ensures your emails actually reach inboxes—not spam folders.

If you care about deliverability, reputation, and scalability, SMTP relay is not just an option—it’s a requirement.