SMTP using net/mail with STARTTLS

## 1. Mail Configuration

When we have certificates for our SMTP servers, the **TLSSkipVerify** should be set to true. Otherwise, set to false

``` golang
// MailConfig contains all configuration for mail
type MailConfig struct {
	AuthMailAddr  string
	AuthPassword  string
	SendFrom      string
	SMTPHost      string
	TLSSkipVerify bool
}

var config MailConfig

func SendMail(mailto string, subject string, body string) error {
    // Code
}
```

## 2. Set From and To

``` golang
	from := mail.Address{
		Name:    "",
		Address: config.SendFrom,
	}
	to := mail.Address{
		Name:    "",
		Address: mailto,
	}
```

## 3. Setup Header and Message

``` golang
    // Setup headers
	headers := make(map[string]string)
	headers["From"] = from.String()
	headers["To"] = to.String()
	headers["Subject"] = subject

// Setup message
	message := ""
	for k, v := range headers {
		message += fmt.Sprintf("%s: %s\r\n", k, v)
	}
	message += "\r\n" + body
```

## 4. Start Connection

``` golang
	// Connect to the SMTP Server
	host, _, _ := net.SplitHostPort(config.SMTPHost)

auth := smtp.PlainAuth("", config.AuthMailAddr, config.AuthPassword, host)

// TLS config
	tlsconfig := &tls.Config{
		InsecureSkipVerify: config.TLSSkipVerify,
		ServerName:         host,
	}
	
    c, err := smtp.Dial(config.SMTPHost)
	if err != nil {
		log.Panic(err)
	}

c.StartTLS(tlsconfig)
```

## 5. Auth and Send Data

``` golang
    // Auth
	if err = c.Auth(auth); err != nil {
		return err
	}

// To && From
	if err = c.Mail(from.Address); err != nil {
		return err
	}

if err = c.Rcpt(to.Address); err != nil {
		return err
	}

// Data
	w, err := c.Data()
	if err != nil {
		return err
	}

_, err = w.Write([]byte(message))
	if err != nil {
		return err
	}

err = w.Close()
	if err != nil {
		return err
	}

c.Quit()
```

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