How to send an e-mail from Go - email

Question

I'm trying to send an e-mail in Golang and I have a lot of problems with it. I'm new in Go so maybe this is very simply but I cannot find the answer on the doc.
This is what I want to do:
1. get an e-mail from the STDIN
2. parse the e-mail (getting from, to, subject, attachments and so on)
3. send this e-mail (put it again to the queue in local postfix)
I did 1 and 2 but I have a problem with 3th one.
This is what I have now:
package main
import (
"fmt"
"github.com/jhillyerd/go.enmime"
//"github.com/sendgrid/sendgrid-go"
"net/smtp"
"github.com/jordan-wright/email"
"os"
"net/mail"
"io/ioutil"
"bytes"
)
func main() {
mail_stdin, err := ioutil.ReadAll(os.Stdin)
if err != nil {
return
}
// Convert type to io.Reader
buf := bytes.NewBuffer(mail_stdin)
msg, err := mail.ReadMessage(buf)
if err != nil {
return
}
mime, err := enmime.ParseMIMEBody(msg)
if err != nil {
return
}
# saving attachments
for _, value := range mime.Attachments {
fmt.Println(value.FileName())
err := ioutil.WriteFile(value.FileName(), value.Content(), 0664)
if err != nil {
//panic(err)
return
}
fmt.Printf("From: %v\n", msg.Header.Get("From"))
fmt.Printf("Subject: %v\n", mime.GetHeader("Subject"))
fmt.Printf("Text Body: %v chars\n", len(mime.Text))
fmt.Printf("HTML Body: %v chars\n", len(mime.Html))
fmt.Printf("Inlines: %v\n", len(mime.Inlines))
fmt.Printf("Attachments: %v\n", len(mime.Attachments))
fmt.Println(mime.Attachments)
fmt.Println(mime.OtherParts)
fmt.Printf("Attachments: %v\n", mime.Attachments)
}
I already did few tests using: net/smtp, sendgrid-go and jordan-wright/email.
All I want to do is to send an e-mail (without changing anything) from the server to the queue again. Most of those modules needs to have Auth, but I just want to simply send is using sendmail, in the same way as I can do this from the bash:
# echo "test" | mail {address}

Answer 1

Using net/smtp you can do this fairly easily... Assuming you have an smtp server running that you can connect to without authentication. I would guess for what you're trying to accomplish it's actually a lot easier to do through something simple like your gmail ( https://www.digitalocean.com/community/tutorials/how-to-use-google-s-smtp-server )
Anyway, here's a couple code samples to cover either case;
c, err := smtp.Dial("mail.example.com:25")
if err != nil {
log.Fatal(err)
}
defer c.Close()
// Set the sender and recipient.
c.Mail("sender#example.org")
c.Rcpt("recipient#example.net")
// Send the email body.
wc, err := c.Data()
if err != nil {
log.Fatal(err)
}
defer wc.Close()
buf := bytes.NewBufferString("This is the email body.")
if _, err = buf.WriteTo(wc); err != nil {
log.Fatal(err)
}
Alternatively here's a go playground example that uses simple auth; http://play.golang.org/p/ATDCgJGKZ3 unless you've already got an smtp server running on your dev box following something like that will probably be a lot easier.