Request an example code for smtp relay about go-smtp

[emersion]

Sorry, but I don't have time for this.

[olljanat]

In case someone is still interested. This is version which I got from ChatGPT:

package main

import (
	"io"
	"log"

	smtp "github.com/emersion/go-smtp"
)

// Backend defines your backend to handle SMTP sessions.
type Backend struct{}

// NewSession is called after client greeting (EHLO, HELO).
func (bkd *Backend) NewSession(c *smtp.Conn) (smtp.Session, error) {
	session := &Session{
		from: "",
		to:   []string{},
	}
	return session, nil
}

// Session is used to store state of an SMTP session through the authentication and message sending process.
type Session struct {
	from string
	to   []string
}

// AuthPlain allows all credentials.
func (s *Session) AuthPlain(username, password string) error {
	return nil
}

func (s *Session) Mail(from string, opts *smtp.MailOptions) error {
	log.Println("Mail from:", from)
	s.from = from
	return nil
}

func (s *Session) Rcpt(to string, opts *smtp.RcptOptions) error {
	log.Println("Rcpt to:", to)
	s.to = append(s.to, to)
	return nil
}

func (s *Session) Data(r io.Reader) error {
	log.Println("Starting to read email data...")
	// Example of sending the email, replace with actual sending logic
	err := smtp.SendMail("smtp.example.com:25", nil, s.from, s.to, r)
	if err != nil {
		log.Printf("Failed to send email: %v\n", err)
		return err
	}

	log.Println("Email sent successfully.")
	return nil
}

func (s *Session) Reset() {
	log.Println("Resetting session")
}

func (s *Session) Logout() error {
	log.Println("Logging out")
	return nil
}

func main() {
	be := &Backend{}

	s := smtp.NewServer(be)

	s.Addr = ":1025"
	s.Domain = "localhost"
	s.AllowInsecureAuth = true

	log.Println("Starting SMTP server on port 1025")
	if err := s.ListenAndServe(); err != nil {
		log.Fatal(err)
	}
}

and it should do the trick.