Regex vs. The Divine: A Case Study in Email Validation and Evangelism

July 2, 2025

admin

“In the beginning was the Word, and the Word was malformed.”

Prologue: In the Valley of Invalid Emails

Every technologist has had their burning bush moment. Mine came not on Mount Sinai, but in a dev environment, knee-deep in bounced emails. Somewhere between test@localhost and user@domain..com, I began to question the very nature of form, of syntax, of whether the universe truly wanted me to validate email addresses—or simply suffer.

Thus began my pilgrimage into the esoteric rites of regex. And as it turns out, regex isn’t a tool—it’s a religion.

Chapter I: And God Said, Let There Be RFC 5322

Most devs begin their journey innocently. A simple requirement: “Just make sure the user types in a valid email.”

They Google: regex for email.

They find… this:

(?:[a-z0-9!#$%&'*+/=?^_`{|}~-]+(?:\.[a-z0-9!#$%&'*+/=?^_`{|}~-]+)*|"(?:[\x01-\x08\x0b\x0c\x0e-\x1f\x21\x23-\x5b\x5d-\x7f]|\\[\x01-\x09\x0b\x0c\x0e-\x7f])*")@(?:(?:[a-z0-9](?:[a-z0-9-]*[a-z0-9])?\.)+[a-z0-9](?:[a-z0-9-]*[a-z0-9])?|\[(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?|[a-z0-9-]*[a-z0-9]:(?:[\x01-\x08\x0b\x0c\x0e-\x1f\x21-\x5a\x53-\x7f]|\\[\x01-\x09\x0b\x0c\x0e-\x7f])+)\])

This is not code.
This is Scripture.

The kind only interpreted by those anointed in the holy trinity of lookaheads, backreferences, and catastrophic backtracking.

Chapter II: The Heresies of Simplicity

You’ll hear whispers in the back pews of Stack Overflow:

“You don’t need full RFC 5322 compliance.”

“Just check for @ and a ..”

“Why not just send a confirmation email and call it a day?”

Heresy. All of it.

Because one day—mark my words—you’ll deploy. And on that day, a QA analyst named Jared will enter user@[192.168.0.1], and your frontend will implode like a dying star.

Chapter III: The Saints and Their Libraries

Blessed are those who reach for libraries, for theirs is the kingdom of maintainability.

In Python, one might invoke the sacred name:

from email_validator import validate_email, EmailNotValidError

try:
    v = validate_email("example@foo.bar")
    email = v.email
except EmailNotValidError as e:
    print(str(e))

In JavaScript:

import validator from 'validator';

if (validator.isEmail('someone@example.com')) {
  // proceed
}

Languages vary, but the path is the same: Stop rolling your own regex. Let the prophets do their work.

Chapter IV: Evangelism by Failure Log

You want your stakeholders to listen? Don’t show them charts. Show them logs:

[ERROR] Invalid email: user@domain..com
[ERROR] Invalid email: blank@.com
[ERROR] Invalid email: not-even-close

Each line is a sermon. Each error a lost soul in need of proper formatting.

Chapter V: Baptism by Bounce

If all else fails, verify with SMTP pingbacks. But beware: you are now contacting the actual mail servers. This is no longer theology—it’s diplomacy.

# Email validation using SMTP (simplified, not always recommended)
from validate_email_address import validate_email

validate_email('test@example.com', verify=True)  # Will ping MX records

Use it sparingly, like a confessional booth in the cloud.

Final Revelation: Salvation Lies in Context

Regex isn’t bad. It’s just… misunderstood. Like the Book of Revelation or Kubernetes YAML files. Use it for good. Don’t chase the one true pattern. Chase clarity. Chase user experience. And when in doubt, remember:

“Let he who has never written .+@.+\..+ cast the first exception.”

Epilogue: Blessed Be the Validators

This post was brought to you by one too many support tickets.

Go forth and sanitize. 🕊