An email relay service is a system that sends outgoing emails on your behalf by routing them through a trusted third-party mail server instead of sending them directly from your own server or application. It acts as a middleman between your website, app, or email client and the recipient’s inbox, ensuring emails are delivered securely and reliably, with a much higher chance of reaching the inbox rather than spam.
How an Email Relay Service Works
At a basic level, an email relay service handles the “sending” part of email delivery.
Here’s a simplified flow:
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Your website, app, or email client creates an email
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Instead of sending it directly to the recipient’s mail server, it sends it to the email relay service
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The relay service authenticates the email
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The relay service delivers the email to the recipient’s server using trusted infrastructure
Because relay services have established reputations, proper authentication, and optimized servers, emails are far more likely to be delivered successfully.
Why Direct Email Sending Often Fails
Many beginners assume emails can be sent directly from a hosting server or VPS. While technically possible, this often causes problems:
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IP addresses are not trusted
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No proper SPF, DKIM, or DMARC setup
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Emails get flagged as spam
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Servers get blacklisted
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ISPs block outgoing mail ports (like port 25)
An email relay service solves these issues by sending emails through pre-approved, reputable servers.
Key Features of an Email Relay Service
1. SMTP Relay
Email relay services provide SMTP credentials that your app or server uses to send emails securely.
2. Authentication & Security
They support:
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SPF
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DKIM
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DMARC
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TLS/SSL encryption
This protects against spoofing and improves inbox placement.
Read More: What Is an Email Relay Service?
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