Send Email With Go and MailJet

The following steps show how to send mail with Go using the standard smtp package. To test I used MailJet as the mail server but you can also use Mandrill or SendGrid.

First let’s setup MailJet as the mail server. Then write the Go code and send a test email.

MailJet Setup

After creating your free MailJet account, you should make sure you complete the 2 steps below (under Account Settings):

Add a Sender Domain or Address
Setup SPF/DKIM Authentication

Personally, I found validating an entire domain very convenient. That way I can use the domain for all my projects mail sending requirements. For example:

project-1@mydomain.com
project-2@mydomain.com
…
project-n@mydomain.com

But you don’t have to use a custom domain if you don’t want to. You can add a single sender email address from which the mail will be sent from.

Next, you need to setup an API key and Secret – these will be the username and password in Go code. You can set the API key and Secret under Account Settings:

Go Code

Please make sure you specify the following constants and variables with your own:

username, password: These are your API key and secret
host, port: the port should be 587, you can find your host under your account settings:

from: the email address from which mail will be sent from. I presume you have set this in the steps above under MailJet account settings: Add a Sender Domain or Address, Setup SPF/DKIM Authentication.
to: you can specify any address that you own for testing. The test email will be sent to this address. I specified my own personal email address which you should replace with your own.

Type the following code in your favorite editor, then run the code in a terminal: go run main.go

package main

import (
	"fmt"
	"log"
	"net/smtp"
	"time"
)

func main() {
	const (
		username = "XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX" // your 32 digit API key
		password = "XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX" // your 32 digit secret
		host     = "XXX.mailjet.com"                  // your MailJet host
		port     = "587"                              // recommended port for TLS
		from     = "FROM-EMAIL@YOUR-VALID-DOMAIN.COM" // your validated domain
		addr     = host + ":" + port
	)

	to := []string{
		"TO-RECIPIENT-EMAIL@DOMAIN.COM",
	}
	subject := "Test mail using Go with MailJet"
	message := fmt.Sprintf(`Subject:%s
Hi,

This is a test message sent with Go and MailJet.

Thanks!

Sent on %v`, subject, time.Now())

	auth := smtp.PlainAuth("", username, password, host)
	err := smtp.SendMail(addr, auth, from, to, []byte(message))
	if err != nil {
		log.Println("send mail:", err)
		return
	}
	fmt.Println("mail sent successfully")
}

If you configured everything correctly and ran the code, you should receive an email like the one shown in the screenshot below. I received my test email at my personal Gmail address. My from address was: “test-project@dovetail.one”