Email Server Security Best Practices

Email remains a primary attack vector for phishing, malware, and spam. Properly securing your email infrastructure is essential for organizational security.

Email-Based Threats

Your email server faces multiple threats:

• Inbound Spam - Unwanted emails consuming resources and potentially carrying malware
• Phishing Attempts - Fraudulent emails designed to steal credentials or sensitive information
• Spoofing Attacks - Attackers impersonating your domain to send fraudulent emails

Email Authentication

Implement these standards to protect your domain:

SPF (Sender Policy Framework)

SPF specifies which mail servers are authorized to send email for your domain. Recipients can verify the sending server is legitimate.

DKIM (DomainKeys Identified Mail)

DKIM adds a digital signature to emails, proving they haven't been modified in transit and originated from your domain.

DMARC

DMARC builds on SPF and DKIM, specifying how receivers should handle emails that fail authentication checks.

Inbound Filtering

Layer multiple filtering techniques:

• IP Reputation (DNSBL) - Reject or flag emails from IPs with poor reputation before processing content
• Content Filtering - Scan message content for spam patterns, malware, and phishing indicators
• Rate Limiting - Limit messages per connection to prevent spam floods