SMTP Relay

How Does an SMTP Relay Work?

An SMTP relay works by acting as a middleman between your application and the recipient’s mail server. When your website or app needs to send an email, it connects to an SMTP relay service rather than delivering the message directly.

Here’s the process, step by step: Your application connects to the SMTP relay server using your credentials (typically a username and password or an API key). Once authenticated, your application hands off the email to the relay server. The relay then takes responsibility for delivering the message.

The relay server handles all the complex parts of email delivery, verifying DNS records, managing retries for temporary failures, and maintaining a strong sender reputation.

Throughout this process, the relay service tracks delivery status and provides you with detailed logs and analytics about your emails.

Why Use an SMTP Relay Instead of Your Own Server?

Using an SMTP relay service offers several important advantages over sending emails directly from your own server.

The biggest benefit is improved deliverability. Web hosting servers often have poor sender reputations because many websites on shared hosting send spam. When you send emails directly from your web server, mail providers may automatically filter your messages as spam, even if they’re legitimate. An SMTP relay service maintains dedicated IP addresses with strong reputations, dramatically improving your chances of reaching the inbox.

SMTP relay services also handle technical complexities for you. They ensure proper SPF, DKIM, and DMARC authentication, manage bounce handling, and automatically retry failed deliveries. These tasks would require significant technical expertise and ongoing maintenance if you handled them yourself.

How Do I Connect to an SMTP Relay?

Connecting to an SMTP relay is straightforward. You’ll need a few pieces of information from your SMTP relay provider. Then you’ll configure your application or email plugin to use those settings.

Here’s what you’ll typically need:

• SMTP server address – The hostname of the relay server (e.g., smtp.sendlayer.net)
• Port number – Usually 587 for TLS or 465 for SSL
• Authentication credentials – Your username and password or API key
• Encryption method – TLS or SSL for secure connections

For WordPress sites, the easiest way to connect is to use a plugin such as WP Mail SMTP or Easy WP SMTP. These plugins provide a simple interface for entering your SMTP credentials without touching any code.

For custom applications, you’ll configure your email library or framework to use the SMTP relay settings. Most modern programming languages have built-in support for SMTP, making integration straightforward whether you’re using Python, PHP, JavaScript, or another language.

Before sending production emails, it’s important to verify your domain and configure your DNS records. This establishes trust with email providers and ensures optimal deliverability.