发送SMTP电子邮件给多个收件人

Question

I am using this to send smtp. It works for one receiver but I'd like to have multiple receivers. I have tried the following:

func sendemail(body string) {  
    from := "smtpemail" 
    pass := "pass"
    to := "[e-mail],[e-mail]"
    ....
}

I have also tried:

to := "\"[e-mail]\",\"[e-mail]\""

and:

to := []string{"[e-mail]","[e-mail]"}

None of them work. Sorry it is so simple, I just begin to work with golang.

Answer 1

From the net/smtp docs:

The msg parameter should be an RFC 822-style email with headers first, a blank line, and then the message body. The lines of msg should be CRLF terminated. The msg headers should usually include fields such as "From", "To", "Subject", and "Cc".

RFC 822 requires To: header value to be a comma separated list. So while the to variable should remain a []string and be passed to smtp.SendMail as its to parameter, the mail header (in the message) should have it as a comma separated list. Try below to see if it works:

func send(body string) {
    // ...
    to := []string{"[e-mail]", "[e-mail]"}
    toHeader := strings.Join(to, ",")

    msg := "From: " + from + "
" +
        "To: " + toHeader + "
" + // use toHeader
        "Subject: Hello there

" +
        body

    err := smtp.SendMail("smtp.gmail.com:587",
        smtp.PlainAuth("", from, pass, "smtp.gmail.com"),
        from, to, []byte(msg))

    // ...
}