Prevent Duplicate Gmail Accounts Securely

Important Warning Before We Start
This topic is for awareness and security purposes only.
It’s not about breaking websites or abusing signup systems
The goal is to help you, as a developer, understand the problem and fix it the right way

The Problem: Multiple Accounts Using the Same Email ​

One of the most common issues in user registration systems is allowing users to create multiple accounts with the same email
The main reason behind this issue is how Gmail handles email addresses.
Google ignores dots (.) in Gmail usernames.
For example, if your email is: example@gmail.com
You can also use:

• e.xample@gmail.com
• ex.ample@gmail.com
• exam.ple@gmail.com
• e.x.a.m.p.l.e@gmail.com

All of them go to the same inbox
However, most databases treat these as different emails, so validation passes without any problem.

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Why This Is a Serious Security Risk ​

Allowing duplicate email registrations can lead to:

• Fake and spam accounts
• Unnecessary server resource usage
• Abuse of free trials and bonuses
• Broken referral or reward systems

That’s why this issue must be handled properly

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The Correct Way to Prevent Duplicate Accounts ​

Let’s solve this problem step by step as developers

Block Temporary (Disposable) Email Addresses​

Temporary email services are a huge risk if left unchecked

The Solution​

Use a ready-made package with a large and updated database of disposable email domains
https://github.com/Propaganistas/Laravel-Disposable-Email

Why This Works​

• Over 135,000 disposable email domains
• Regularly updated

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Automatically Update the Disposable Email List​

To keep the list always up to date, schedule a weekly update using Cron:

$schedule->command('disposable:update')->weekly();

This ensures fake and temporary emails are blocked automatically.

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Normalize Gmail Emails by Removing Dots​

This is the most important step
Before validation or saving the email to the database, you must clean Gmail addresses.

The Idea ​

For any Gmail address:

• Remove all dots (.)
• Store the normalized email in the database

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PHP Example: Gmail Email Normalization ​

$email = strtolower($request->email);

if (str_contains($email, '@gmail.com')) {
    [$name, $domain] = explode('@', $email);
    $name = str_replace('.', '', $name);
    $email = $name . '@' . $domain;
}

Result:

• example@gmail.com
• e.xa.mple@gmail.com

Both are treated as one email in the database

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Protect Your Signup System from Bots ​

Even after fixing email issues, bots are still a threat.
The simplest and most effective solutions include:

• Google reCAPTCHA
• Cloudflare Turnstile
• Any reliable bot detection system

This helps prevent:

• Automated registrations
• Spam accounts
• Brute-force attacks

And honestly… it saves a lot of headaches

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Final Summary ​

If you run a user registration system, make sure to:

• Block disposable email addresses
• Normalize Gmail emails (remove dots)
• Enable bot protection

This guarantees a clean, secure, and abuse-free signup system
And that’s a core foundation for any successful website