go - 如何通过 `exim -t` 发送密件抄送电子邮件？ ["sendmail look alike"模式]

Question

我正在使用 golang 通过以下方法通过 exim 发送电子邮件

const sendmail = "/usr/sbin/exim"

func submitMail(m *gomail.Message) (err error) {
    cmd := exec.Command(sendmail, "-t")
    cmd.Stdout = os.Stdout
    cmd.Stderr = os.Stderr

    pw, err := cmd.StdinPipe()
    if err != nil {
        return
    }

    err = cmd.Start()
    if err != nil {
        return
    }

    var errs [3]error
    _, errs[0] = m.WriteTo(pw)
    errs[1] = pw.Close()
    errs[2] = cmd.Wait()
    for _, err = range errs {
        if err != nil {
            return
        }
    }
    return
}

as Answered on here

问题是 Exim 使用 -t

删除了 Bcc

If Exim is called with the -t option, to take recipient addresses from a message's headers, it removes any Bcc: header that may exist (after extracting its addresses), unless the message has no To: or Cc: header, in which case a Bcc: header with no addresses is left in the message, in accordance with RFC 822. If -t is not present on the command line, any existing Bcc: header is not removed.

If Exim is called to receive a message with the recipient addresses given on the command line, and there is no Bcc:, To:, or Cc: header in the message, it normally adds a To: header, listing the recipients. Some mailing list software is known to submit messages in this way, and in this case the creation of a To: header is not what is wanted. If the always_bcc option is set, Exim adds an empty Bcc: header instead in this circumstance.

found in Spec here

Answer 1

-t 的“Sendmail look alike”模式删除 Bcc: header 处理后。
在 -t 模式下 Bcc: header 内容将附加到 (SMTP) 收件人列表中 BUT 收件人将看不到/接收 Bcc : header 。

风格指南建议:如果您在“sendmail look alike”(命令行比较模式)中使用另一个 SMTP/MTA 软件(例如 Exim)那么 使用他们提供的 sendmail 程序/二进制文件。
const sendmail = "/usr/sbin/sendmail"