emailvalidation.go

package main

import (
	"fmt"
	"net"
	"regexp"
	"strings"
)

var emailRegex = regexp.MustCompile("^[a-zA-Z0-9.!#$%&'*+\\/=?^_`{|}~-]+@[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?(?:\\.[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?)*$")

func isEmailValid(email string) bool {
	if len(email) < 3 || len(email) > 254 {
		return false
	}
	if !emailRegex.MatchString(email) {
		return false
	}
	parts := strings.Split(email, "@")
	mx, err := net.LookupMX(parts[1])
	if err != nil || len(mx) == 0 {
		return false
	}
	return true
}

func main() {
	if e := "test@gophers1.cz"; !isEmailValid(e) {
		fmt.Println(e + " isn't a valid email")
	}
}