How do corporate/enterprise filters behave differently from consumer ISPs?

Corporate/enterprise filters:

• Barracuda, Proofpoint, Mimecast, Microsoft Defender
• Often more aggressive blocking
• Policy-based rules (no marketing from unknown senders)
• Less engagement-based, more rule-based
• Company-specific configurations

Consumer ISPs:

• Gmail, Yahoo, Outlook.com
• More engagement and reputation focused
• ML-based filtering
• More uniform behavior across users

Implications:

• B2B mail faces different challenges than B2C
• Good consumer reputation does not guarantee corporate delivery
• Corporate filters may need direct relationship or whitelisting
• Commercial ports have different inspection standards than private harbors.