On Sun, Jun 29, 2008 at 07:55:07AM -0700, Roger Marquis wrote:

Quoting <http://www.postconf.com/docs/spamrep/> :

The only reliable way to avoid false-positives is by monitoring the email server or gateway logs and allowing end-users to receive a daily report of email sent to their account that was identified as spam and filtered.

Two comments: First, it is impossible to avoid false positives (unless you turn all spam filtering off) or false negatives (unless you block everything). The discussion thus shouldn't focus on 0% FP, 0% FN, but on how to minimize both simultaneously such that the percentages are acceptable to the receiving organization. (Note as well that FP and FN are always defined on recipient side, never the sender side.) Second, while in principle this isn't a bad approach, in reality it tends not to work well. It requires that users weed through the daily reports (which they won't) and determine what's spam/not-spam (which they'll get wrong) and it requires accepting and storing considerable volumes of mail which are likely spam/phish/virus/etc. It also can make FP detection difficult, since senders do not get a reject (mail was accepted, after all; why should they?) and thus may be unaware that their message was dropped in a probable-spam folder. I find it's much better to reject outright with a very clear error message (that provides recourse for senders who believe it to be in error) and then address the resulting issues at the postmaster level (since in most environments such issues are likely to effect more than one user). ---Rsk