Anti-spam techniques.

• Spam Harassment Reduction
• Bonds or Sender-at-risk
• Proof-of-work systems
• Techniques for researchers & law enforcement
• Techniques for researchers & law enforcement
• Spam report feedback loops
• Port 25 interception
• Port 25 blocking
• Limit e-mail backscatter&Egress spam filtering
• Confirmed opt-in for mailing lists
• Background checks
• X-ASVP&Automated techniques
• Tarpits&Transparent SMTP proxy
• Statistical content filtering
• MTP callback verification
• Sender-supported whitelists and tags
• Rule-based filtering
• PTR/Reverse DNS checks
• Greeting delay & Hybrid filtering
• Fake MX Records
• Greylisting
• HELO/EHLO checking
• Enforcing RFC standards
• DNS-based Blackhole
• Country-based filtering
• Checksum-based filtering
• Challenge/response systems
• Automated techniques for e-mail administrators
• Reporting spam
• Disposable e-mail addresses
• Disable HTML in e-mail
• Contact Forms
• Avoid responding to spam
• Address munging
• Anti-spam