554, b'5.0.0 Error: transaction failed, blame it on the weathe about go-smtp

[foxcpp]

		u := strings.Split(user, "@")
		host := "smtp." + u[1] + ":465"
		auth := sasl.NewPlainClient("", "", "")
		err = smtp.SendMail(host, auth, s.from, []string{user}, r)
		if err != nil {
			fmt.Println(err)
			return err
		}

You try to read r after already reading it completely above (using ioutil.ReadAll).

[foxcpp]

Closing as this is not a problem in go-smtp. I suggest you to attempt some basic troubleshooting before asking other people to do your work.