Well the numbers I am seeing are totally unreliable anyway (for blocking spam at least). I see valid emails at 1.0 and spam at .99 or that doesn't get hit at all.
I was just wondering the meanings and maybe trying to dive a little deeper into their methodology. SpamAssassin seems to be much more efficient as far as giving email a ranking. On Tue, 03 Jun 2003 15:31:15 -0400, you wrote: > >> > Specifically, what the numbers mean. I am seeing .9xxx and 1.000 in the >> > header. Does this mean 97% chance it is spam and 1.00 is a 100% chance it >> > is spam? >> >> > X-IMAIL-SPAM-STATISTICS: 0.9787 > >>You are correct. > >Actually (Ipswitch can correct me if I am wrong), this is not a true >probability but a "pseudo-probability" (a number between 0 and 1 that acts >like a probability, but isn't one). With naive Bayes theorem, for example, >you will often get E-mails that show a 99.9999% chance of being spam >(that's 1 in 1 million chance), whereas the real probability might really >be something like 99.8% chance (1 in 500 chance). Naive Bayes Theorem >essentially simulates extremely complex calculations (too complex to be >done in real-time), and ends up coming up with estimates that are normally >very close numerically to the actual probabilities. > >In some situation, exact probabilities are much better than estimates. For >example, with web hosting, the difference between 99.5% uptime and 99.99% >uptime is drastic. However, for spam control, the difference between 99.5% >and 99.99% isn't very important (since many people would delete the E-mail >in either case). In this case, estimates are much more acceptable. > >The key here is not to run any true statistical calculations based on the >number you see (for example, don't assume that if you see 1.0000, that you >will have a 0% false positive ratio, or that with .9990 you'll have 30 >false positives a month if you process 1,000 E-mails/day). > > -Scott >--- >Declude JunkMail: The advanced anti-spam solution for IMail mailservers. >Declude Virus: Catches known viruses and is the leader in mailserver >vulnerability detection. >Find out what you have been missing: Ask for a free 30-day evaluation. > >--- >[This E-mail was scanned for viruses by Declude Virus (http://www.declude.com)] > > >To Unsubscribe: http://www.ipswitch.com/support/mailing-lists.html >List Archive: http://www.mail-archive.com/imail_forum%40list.ipswitch.com/ >Knowledge Base/FAQ: http://www.ipswitch.com/support/IMail/ To Unsubscribe: http://www.ipswitch.com/support/mailing-lists.html List Archive: http://www.mail-archive.com/imail_forum%40list.ipswitch.com/ Knowledge Base/FAQ: http://www.ipswitch.com/support/IMail/
