## Can You Bypass SMTP Servers for Bulk Emailing in Go?

Sending Emails without SMTP Servers in Go

Question:

Is it possible to send bulk emails without using third-party SMTP servers? Can the standard library's SMTP package provide a solution?

Answer:

Directly sending emails without an SMTP server is not feasible. However, you can utilize other programs that have email-sending capabilities.

Approach Using External Programs:

One recommended approach is to leverage external programs like Sendmail or Nullmailer. These programs handle email delivery and can be invoked using the os/exec package in Go.

Specifically, you can use the WriteTo method of the gomail.Message type to send emails directly to a running Sendmail instance. Here's an example code snippet:

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

    "github.com/gomail/gomail"
)

func submitMail(m *gomail.Message) (err error) {
    const sendmail = "/usr/sbin/sendmail"

    cmd := exec.Command(sendmail, "-t")
    cmd.Stdout = os.Stdout
    cmd.Stderr = os.Stderr

    pw, err := cmd.StdinPipe()
    if err != nil {
        return
    }

    err = cmd.Start()
    if err != nil {
        return
    }

    var errs [3]error
    _, errs[0] = m.WriteTo(pw)
    errs[1] = pw.Close()
    errs[2] = cmd.Wait()
    for _, err = range errs {
        if err != nil {
            return
        }
    }
    return
}</code>

Advantages of Using MTAs:

While not directly related to SMTP server usage, utilizing full-blown Mail Transfer Agents (MTAs) like Sendmail offers additional benefits. MTAs provide mail queuing, ensuring that emails are reliably delivered even in case of network outages.

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