Golang : Normalize email to prevent multiple signups example

If your application allows the public to sign up, chances are your application will attract the "unkind" types and they will attempt to sign up multiple times with the same email address by mixing symbols, upper and lower cases and adding dots to make variants of the same email address.

To prevent this sort of multiple sign ups, you can try to normalize(canonicalize - treat them as the same) the email addresses by removing the unwanted cases, symbols,etc. Below is an example of how to normalize email address with govalidator.NormalizeEmail() function.

At this moment, the NormalizeEmail() function only supports gmail.com accounts. You might want to see the source code in govalidator package to modify it for your own requirement.

 package main

 import (

 func main() {
 email := "sammy+SPammer@gmail.com"

 normalized, err := govalidator.NormalizeEmail(email)

 if err != nil {

 log.Println("Before : ", email)

 log.Println("Normalized email : ", normalized)


Output :

NOTE : IF gmail, anything after + symbol will be removed

2015/08/11 14:43:28 Before : sammy+SPammer@gmail.com

2015/08/11 14:43:28 Normalized email : sammy@gmail.com

change to another domain name, the result will be different.

2015/08/11 14:51:18 Before : sammy+SPammer@somewhere.com

2015/08/11 14:51:18 Normalized email : sammy+spammer@somewhere.com

Reference :


By Adam Ng

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