Email with Plus Addressing Regex for Python

What this pattern does

This page provides a comprehensive, battle-tested regular expression for matching email with plus addressing, ported and verified for Python. A rigorously tested regex reduces debugging time and protects your application from edge-case failures. The snippet below is ready to drop into your Python project — whether you're validating in a Django view, a FastAPI endpoint, or a standalone data processing script.

Python Implementation

# Email with Plus Addressing
# ReDoS-safe | RegexVault — Web & Network > Misc

import re

email_with_plus_addressing_pattern = re.compile(r'^([a-zA-Z0-9.!#$%&'*/=?^_`{|}~\-]{1,64})\+([a-zA-Z0-9.\-_]{1,64})@([a-zA-Z0-9](?:[a-zA-Z0-9\-]{0,61}[a-zA-Z0-9])?(?:\.[a-zA-Z0-9](?:[a-zA-Z0-9\-]{0,61}[a-zA-Z0-9])?)*)$')

def validate_email_with_plus_addressing(value: str) -> bool:
    return bool(email_with_plus_addressing_pattern.fullmatch(value))

# Example
print(validate_email_with_plus_addressing("user+tag@example.com"))  # 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 Python developers because particularly important in Python web servers where CPU-bound regex operations can stall concurrent request handling. 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

Capture group 1: local base, group 2: plus tag, group 3: domain. Use to detect sub-addressing and optionally strip the tag before lookup. Gmail, Outlook, and Fastmail support plus addressing.