Email Security

SPF, DKIM, DMARC, email filtering, and phishing prevention.

Overview

Email security protects against spam, phishing, and malware.

Email Authentication

SPF (Sender Policy Framework)

example.com. IN TXT "v=spf1 mx ip4:192.168.1.0/24 -all"

DKIM (DomainKeys Identified Mail)

selector._domainkey.example.com. IN TXT "v=DKIM1; k=rsa; p=MIGfMA0G..."

DMARC (Domain-based Message Authentication)

_dmarc.example.com. IN TXT "v=DMARC1; p=reject; rua=mailto:admin@example.com"

Email Filtering

# Spam detection
def check_spam(email):
    spam_score = 0
    
    # Check sender reputation
    if email.sender in blacklisted_senders:
        spam_score += 10
    
    # Check content
    spam_words = ['free', 'winner', 'click here']
    for word in spam_words:
        if word in email.body.lower():
            spam_score += 1
    
    return spam_score > 5

Email Security Gateway

Phishing Indicators

Red Flags:
✗ Suspicious sender domain
✗ Urgent action required
✗ Poor grammar/spelling
✗ Unexpected attachments
✗ Suspicious links
✗ Request for credentials

Secure Email Configuration

# SMTP with TLS
import smtplib
from email.mime.text import MIMEText

msg = MIMEText('Secure message')
msg['Subject'] = 'Important'
msg['From'] = 'sender@example.com'
msg['To'] = 'recipient@example.com'

with smtplib.SMTP('smtp.example.com', 587) as server:
    server.starttls()
    server.login('user', 'password')
    server.send_message(msg)

Best Practices

1. Implement SPF/DKIM/DMARC — Prevent spoofing
2. Email encryption — S/MIME, PGP
3. User training — Phishing awareness
4. Attachment filtering — Block dangerous types
5. Link protection — URL scanning

Practice

Configure SPF, DKIM, and DMARC for a domain.