AntiSpam Guide 8.3.8 Prin ted on 27 January, 2006 i Contents Introduction 1 How It Works 3 MIAS Scoring System.................................................................................................................6 Actions.......................................................................................................................................6 Bypassing MIAS.........................................................................................................................7 Spam Folders..............................................................................................................................7 Processing Flow Chart.................................................................................................................8 Administration 12 General configuration.................................................................................................................12 MIAS action configuration.........................................................................................................14 Other Configuration...................................................................................................................15 Statistics....................................................................................................................................17 Configuration Files 18 Bypass Files...............................................................................................................................19 MIAS Properties in Detail..........................................................................................................19 Spam Assassin 21 How It Works.......................................................................................................................................22 SA Scoring System....................................................................................................................22 Reporting Function.....................................................................................................................23 Additional Filters.......................................................................................................................24 Administration......................................................................................................................................25 Configuration Files...............................................................................................................................27 MIAS Properties in Detail..........................................................................................................28 Sender Policy Framework and Sender Rewriting Scheme 29 Administration...........................................................................................................................30 DomainKeys 31 Administration...........................................................................................................................32 ii Contents Greylisting 35 How It Works.......................................................................................................................................36 Administration......................................................................................................................................38 Configuration Files...............................................................................................................................40 Challenge Response 41 How It Works.......................................................................................................................................42 Administration......................................................................................................................................46 Configuration File.................................................................................................................................51 Bayesian Filters 52 How It Works.......................................................................................................................................53 Administration......................................................................................................................................56 Configuration Files...............................................................................................................................58 Body & HTML filters 59 How It Works.......................................................................................................................................60 Body & HTML filters.................................................................................................................60 Charset filters.............................................................................................................................60 Administration......................................................................................................................................62 Configuration Files...............................................................................................................................66 Content Filters 67 How It Works.......................................................................................................................................68 Administration......................................................................................................................................70 Content Filters Export / Import...................................................................................................72 Configuration Files...............................................................................................................................73 Black and White Lists 73 How It Works.......................................................................................................................................74 Administration......................................................................................................................................76 Configuration Files...............................................................................................................................78 Other 78 Tarpitting..............................................................................................................................................79 How it works.............................................................................................................................79 Administration...........................................................................................................................79 Configuration files.....................................................................................................................81 DNSBL................................................................................................................................................82 How it works.............................................................................................................................82 Administration...........................................................................................................................82 Configuration files.....................................................................................................................83 Miscellaneous.......................................................................................................................................85 HELO/EHLO.............................................................................................................................85 Contents iii Delayed SMTP session processing..............................................................................................86 Troubleshooting 87 Engine Logging....................................................................................................................................88 Actions......................................................................................................................................88 Reasons.....................................................................................................................................90 SMTP Test Tool...................................................................................................................................92 FAQs....................................................................................................................................................94 Why Is Spam Message in My Inbox Folder?...............................................................................95 Why Is Legitimate Message in Spam Folder?..............................................................................96 How to check the Automated General Spam Reference Base Update...........................................96 How to Enable SPF....................................................................................................................97 How to customize Challenge Response messages?......................................................................98 How to Stop Spammers Using ESMTP and Demo/Known Accounts...........................................99 How to Use Merak as your AntiSpam and AntiVirus Gateway for MS Exchange Server?..........101 How to enable spam folders for selected users..........................................................................105 How to bypass all local messages from Spam Scanning ?..........................................................106