Golang未经授权发送电子邮件

I am writing a golang program to send a email to my gmail account to report some problem. Here is my code:

c, err := smtp.Dial("aspmx.l.google.com:25")
if err != nil {
    log.Fatal("dial err ", err)
}

if err := c.Mail("report@mbytetech.com"); err != nil {
    log.Fatal("Mail err ", err)
}
if err := c.Rcpt("zing.luke@gmail.com"); err != nil {
    log.Fatal("Rcpt err ", err)
}
wc, err := c.Data()
if err != nil {
    log.Fatal("Data err ", err)
}
_, err = fmt.Fprintln(wc, "In your face, Neil Armstrong")
if err != nil {
    log.Fatal("writer err ", err)
}
err = wc.Close()
if err != nil {
    // log.Fatal(err)
    fmt.Print(err)
    return
}
err = c.Quit()
if err != nil {
    log.Fatal("quit err ", err)
}

I don't actually have a email account as "report@mbytetech.com"(But I do have a gmail account "zing.luke@gmail.com"). I just want it to be shown as "sender" in the email. And my boss told me that he doesn't want to really create a email account to do the "send" work.

Evertime I run this program, it always give me an error said "421 4.7.0 [54.176.117.9 15] Our system has detected an unusual rate of...". And I never got a email in my inbox.

I look up the Google smtp server and Google bulk mail. But I just can't find any solution.

Please someone help me out, I really appreciate that!