package main

import (
  "fmt"
  "net/smtp"
)

const (
  // 郵件服務器地址
  SMTP_MAIL_HOST = "smtp.qq.com"
  // 端口
  SMTP_MAIL_PORT = "587"
  // 發送郵件用戶賬號
  SMTP_MAIL_USER = "1348581672@qq.com"
  // 授權密碼
  SMTP_MAIL_PWD = "xxxx"
  // 發送郵件昵稱
  SMTP_MAIL_NICKNAME = "lewis"
)

func main() {
  //聲明err, subject,body類型，并為address，auth以及contentType賦值， 
  //subeject是主題，body是郵件內容, address是收件人
  
  var err error
  var subject, body string
  address := "lewissunp@outlook.com"
  auth := smtp.PlainAuth("", SMTP_MAIL_USER, SMTP_MAIL_PWD, SMTP_MAIL_HOST)
  contentType := "Content-Type: text/html; charset=UTF-8"

  //要發送的消息，可以直接寫在[]bytes里，但是看著太亂，因此使用格式化
  s := fmt.Sprintf("To:%s\r\nFrom:%s%s>\r\nSubject:%s\r\n%s\r\n\r\n%s",
    address, SMTP_MAIL_NICKNAME, SMTP_MAIL_USER, subject, contentType, body)
  msg := []byte(s)

  //郵件服務地址格式是"host:port"，因此把addr格式化為這個格式，直接賦值也行。
  addr := fmt.Sprintf("%s:%s", SMTP_MAIL_HOST, SMTP_MAIL_PORT)

  //發送郵件
  err = smtp.SendMail(addr, auth, SMTP_MAIL_USER, []string{address}, msg)
  if err != nil {
    fmt.Println(err)
  } else {
    fmt.Println("send email succeed")
  }
}

package main

import (
  "fmt"
  "net/smtp"
)

const (
  // 郵件服務器地址
  SMTP_MAIL_HOST = "smtp.qq.com"
  // 端口
  SMTP_MAIL_PORT = "587"
  // 發送郵件用戶賬號
  SMTP_MAIL_USER = "1348581672@qq.com"
  // 授權密碼
  SMTP_MAIL_PWD = "jhguvicvhrnwgaeh"
  // 發送郵件昵稱
  SMTP_MAIL_NICKNAME = "lewis"
)

func main() {
  address := []string{"norton_s@qq.com", "lewissunp@outlook.com"}
  subject := "test mail"
  body :=
    `br>hello!/br>
  br>this is a test email, pls ignore it./br>`
  SendMail(address, subject, body)

}

func SendMail(address []string, subject, body string) (err error) {
  // 認證, content-type設置
  auth := smtp.PlainAuth("", SMTP_MAIL_USER, SMTP_MAIL_PWD, SMTP_MAIL_HOST)
  contentType := "Content-Type: text/html; charset=UTF-8"

  // 因為收件人，即address有多個，所以需要遍歷,挨個發送
  for _, to := range address {
    s := fmt.Sprintf("To:%s\r\nFrom:%s%s>\r\nSubject:%s\r\n%s\r\n\r\n%s", to, SMTP_MAIL_NICKNAME, SMTP_MAIL_USER, subject, contentType, body)
    msg := []byte(s)
    addr := fmt.Sprintf("%s:%s", SMTP_MAIL_HOST, SMTP_MAIL_PORT)
    err = smtp.SendMail(addr, auth, SMTP_MAIL_USER, []string{to}, msg)
    if err != nil {
      return err
    }
  }
  return err
}