Email Address (RFC 5321 Simplified) Regex for PHP

What this pattern does

This page provides a comprehensive, battle-tested regular expression for matching email address (rfc 5321 simplified), ported and verified for PHP. A rigorously tested regex reduces debugging time and protects your application from edge-case failures. The snippet below is ready to drop into your PHP project — whether you're validating in a Laravel validator, a WordPress plugin, or a standalone PHP script.

Php Implementation

<?php
// Email Address (RFC 5321 Simplified)
// ReDoS-safe | RegexVault — Web & Network > Misc

define('EMAIL_ADDRESS_RFC_5321_SIMPLIFIED_PATTERN', '/^[a-zA-Z0-9.!#$%&\'*+\/=?^_`{|}~\-]{1,64}@[a-zA-Z0-9](?:[a-zA-Z0-9\-]{0,61}[a-zA-Z0-9])?(?:\.[a-zA-Z0-9](?:[a-zA-Z0-9\-]{0,61}[a-zA-Z0-9])?)*\.[a-zA-Z]{2,63}$/');

function validate_email_address_rfc_5321_simplified(string $input): bool {
    return (bool) preg_match(EMAIL_ADDRESS_RFC_5321_SIMPLIFIED_PATTERN, $input);
}

// Example
var_dump(validate_email_address_rfc_5321_simplified("user@example.com")); // bool(true)

Test Cases

When to use this pattern

This pattern is drawn from the Web & Network > Misc category and carries a ReDoS-safe certification. That matters for PHP developers because especially relevant in PHP where PCRE backtracking limits can trigger silent failures on malicious input. RegexVault audits patterns against known backtracking attack vectors, ensuring you have the necessary context before using this regex in a high-stakes production environment.

Common Pitfalls

Technical Notes

Full RFC 5321 compliance is extremely complex. This covers 99%+ of real-world email addresses. Local part limited to 64 chars per RFC 5321 section 4.5.3. Always send a confirmation email to verify — regex alone cannot confirm deliverability.