How Can I Send Emails in Go Without Using an SMTP Server?

Sending Emails in Go Without an SMTP Server

You seek to send bulk mail through a Go server application, avoiding potential quota limitations imposed by third-party SMTP servers.

Alternative Approaches

Regrettably, without directly interacting with an SMTP server, sending emails is not feasible.

Delegating to External Programs

To bypass an SMTP server, consider delegating the task to another program capable of sending emails.

On POSIX systems (e.g., Linux), you can typically find utilities like /usr/sbin/sendmail or /usr/bin/sendmail. These programs accept email messages and forward them for delivery.

Using the gomail Library

Simplifying this process, the gomail library provides a User-friendly API for interacting with external email sending utilities like Sendmail.

Here's an example using the gomail package:

<code class="go">import (
    "bytes"
    "os/exec"

    "github.com/go-gomail/gomail"
)

const sendmail = "/usr/sbin/sendmail"

func sendEmail(m *gomail.Message) error {
    cmd := exec.Command(sendmail, "-t")
    cmd.Stdin = bytes.NewReader([]byte(m.Format()))

    if err := cmd.Run(); err != nil {
        return err
    }

    return nil
}</code>

Advantages of Relying on an MTA

While it may seem convenient to handle email sending without an SMTP server, relying on an MTA (Mail Transfer Agent) like Sendmail offers advantages:

• Email Queuing: MTAs provide mail queuing, ensuring messages are delivered even during temporary network outages.

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