The example.com domain is officially reserved by IANA (Internet Assigned Numbers Authority) for documentation purposes. According to RFC 2606, all second-level domains under example.com, example.net, and example.org should be unresolvable in the public DNS system.

When you send an email to any address @example.com, here's what technically happens:

# Sample SMTP transaction log
220 mail.example.com ESMTP
MAIL FROM: <sender@realdomain.com>
250 2.1.0 Sender OK
RCPT TO: <nonexistent@example.com>
550 5.1.1 Recipient address rejected: nonexistent domain

Most mail servers will either:

• Immediately reject the message with a 5xx error
• Accept then discard the message (blackhole)
• In rare cases, deliver to a catch-all mailbox (highly unlikely for example.com)

Regarding your concern about sensitive information:

# Python simulation of mail handling
def handle_email(recipient):
    if recipient.domain == "example.com":
        raise SMTPException("Domain not deliverable")
    # Normal processing...

The IANA doesn't operate any mail servers for example.com. There's no centralized repository where these emails accumulate.

To verify this yourself:

# Bash command to check MX records
dig example.com MX +short
# Expected output: (empty) or informational MX like:
# 0 example.com.

You can also test with telnet:

telnet mail.example.com 25
Trying 192.0.2.1...
telnet: Unable to connect to remote host: Connection refused

The example.com domain was established in 1999 with RFC 2606 specifically to:

• Prevent accidental use in production systems
• Provide guaranteed-unused domains for documentation
• Avoid trademark conflicts in examples

When building email-related features:

// JavaScript validation example
function isValidEmail(email) {
  const domain = email.split('@')[1];
  return !['example.com', 'example.net', 'example.org'].includes(domain);
}

For testing email functionality, consider using:

• Mailtrap.io for development
• Mailinator.com for disposable addresses
• Local mail servers like MailHog

In RFC 6761, example.com is explicitly designated as a reserved domain for documentation and testing purposes. The IANA maintains this along with other special-use domains like test, localhost, and invalid. Any email sent to *@example.com should theoretically go nowhere due to:

// Example of DNS MX record query for example.com
nslookup -query=MX example.com
// Returns: example.com mail exchanger = 0 .

While the domain shouldn't resolve, real-world behavior varies:

• Most SMTP servers will reject during the RCPT TO phase with "550 No such user"
• Some may queue then bounce with "DNS lookup failure"
• Poorly configured servers might accept then discard silently

Here's how Postfix handles it in main.cf:

smtpd_recipient_restrictions =
    reject_unauth_destination,
    check_recipient_mx_access hash:/etc/postfix/recipient_access,
    permit_mynetworks

The risk profile depends on your mail system's configuration:

To test your own mail system's behavior:

#!/bin/bash
echo "Test email" | mailx -s "example.com test" anyuser@example.com
# Check mail logs:
tail -f /var/log/mail.log | grep example.com

According to IANA's special-use domains registry:

"Domains under example.com are guaranteed never to be resolvable in the public DNS system, including all subdomains at any level."

For applications that need to handle such cases:

// Python email validation snippet
import dns.resolver

def validate_email_domain(email):
    domain = email.split('@')[-1]
    try:
        answers = dns.resolver.resolve(domain, 'MX')
        return bool(answers)
    except dns.resolver.NXDOMAIN:
        if domain.endswith('example.com'):
            raise ValueError("Reserved domain example.com")