Simple Mailer Example

This example is the most simple piece of code that is required to successfully send a mail with go-mail.

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package main

import (
	"log"
	"os"

	"github.com/wneessen/go-mail"
)

func main() {
    msg := mail.NewMsg()
    if err := msg.From("toni@tester.com"); err != nil {
        log.Fatalf("failed to set FROM address: %s", err)
    }
    if err := msg.To("tina@recipient.org"); err != nil {
        log.Fatalf("failed to set TO address: %s", err)
    }
    msg.Subject("This is my first test mail with go-mail!")
    msg.SetBodyString(mail.TypeTextPlain, "This will be the content of the mail.") 
    
    // Deliver the mails via SMTP 
    c, err := mail.NewClient("smtp.example.com", 
        mail.WithSMTPAuth(mail.SMTPAuthPlain), mail.WithTLSPortPolicy(mail.TLSMandatory), 
        mail.WithUsername(os.Getenv("SMTP_USER")), mail.WithPassword(os.Getenv("SMTP_PASS")), 
    )
    if err != nil {
        log.Fatalf("failed to create new mail delivery client: %s", err)
    }
    if err := c.DialAndSend(msg); err != nil {
        log.Fatalf("failed to deliver mail: %s", err)
    }
    log.Printf("Test mail successfully delivered.")
}

This example will send a very basic test mail from toni@tester.com to tina@recipient.org.

First, in line 11, we create a new Msg. The Msg type holds everything that is required for your mail message. Think of it like a new mail within your mail user agent. The Msg type provides you with all of the methods that are required to prepare and format your mail message.

In line 12 thru 14 we set the sender address. In this case it’s toni@tester.com. Since go-mail is doing a lot of validation under the hood, it will make sure that the provided mail address is valid. Therefore we check the returned error. In line 15 thru 17 we do the same for the recipient address. The mail will be sent to tina@recipient.org.

Next, in line 18 we set our subject for our mail message. Followed by setting a simple string as message body in line 19. The first argument for Msg.SetBodyString() is a MIME content type. In this case we use mail.TypeTextPlain for the mail body - so a simple plain/text mail body.

Now that our simple mail message is prepared for delivery, we can create a Client. The Client in go-mail handles the connection to a mail server and everything related to it. In line 22 thru 25 we initialize a new Client type and give it some options. The first argument is the mail server we want to connect to. In our example it’s smtp.example.com. Then we tell the Client that we need to perform SMTP Auth via the PLAIN auth method. The mail.WithSMTPAuth(mail.SMTPAuthPlain) option handles this. With the mail.WithTLSPortPolicy(mail.TLSMandatory) option, we tell the Client that we require a TLS connection for sending our mail. We set it to mandatory mode, so that the Client will stop processing if it cannot accomplish a TLS secured connection. With the mail.WithUsername() and mail.WithPassword() options, we let the Client know what username and password to use for the SMTP auth. Lines 26-28 check if the Client invocation worked without errors.

Finally, in line 29-32 we send out our mail message using our mail client with the Client.DialAndSend() method. We print out a brief message on success or throw an error in case the delivery failed.