Unencrypted connection when sending mail using mailhog and golang

Question

These code works normally when using gmail (with AllowLessSecureApp turned on), but doesn't work with mailhog (unencrypted connection error), these the minimal code to reproduce:

package main
import (
    "crypto/tls"
    "fmt"
    "net/smtp"

    "github.com/jordan-wright/email"
    "github.com/stretchr/testify/assert"
)

func TestSendMail(t *testing.T) {
  m := struct{
    Host string
    Port int
    User string
    Pass string 
  }{
    Host: `local.test`, // resolved to 127.0.0.1 in /etc/hosts
    Port: 1025,
    User: `[email protected]`,
    Pass: `test`,
  }
  e := email.NewEmail()
  e.From = `[email protected]`
  e.To = []string{`[email protected]`}
  e.Subject = `test mail`
  host, _ := os.Hostname()
  e.Text = []byte(`testing email from ` + host)
  err := e.SendWithStartTLS(fmt.Sprintf("%s:%d", m.Host, m.Port), smtp.PlainAuth("", m.User, m.Pass, m.Host), &tls.Config{InsecureSkipVerify: true})
  assert.NoError(t, err)
}

The docker-compose.yml:

version: "3.9"
services:
  mailhog:
    image: mailhog/mailhog
    container_name: test_mailhog
    env_file:
      - backend/.env # not used
    ports:
      - 1025:1025 # smtp server
      - 8025:8025 # web ui
    restart: unless-stopped

Or any workaround for this? eg. some TLS proxy on docker-compose?

Answer 1

it is possible that mailhog does not have proper TLS certs, and it listens without TLS on localhost, try using function https://pkg.go.dev/github.com/jordan-wright/email#Email.Send to send email

err := e.Send(fmt.Sprintf("%s:%d", m.Host, m.Port),smtp.CRAMMD5Auth(m.User,m.Pass))