Jim's Blog

1. Mail Configuration

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

// 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

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

3. Setup Header and Message

    // 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

    // 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

    // 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()