On 20240511 14:56:51, Greg Troxel wrote:
Thomas Barth<tba...@txbweb.de> writes:
Am 2024-05-11 21:54, schrieb Bill Cole:
I have no idea who the Debian "spam analysts" are but I am certain
that they are not doing any sort of data-driven dynamic adjustments
of scores based on a threshold of 6.3 nor are they (obviously)
adjusting that threshold daily based on current scores.
I found the passage in my old Postfix book. The author writes: "It is
recommended not to carelessly set the value of $sa_kill_level_deflt to
any fantasy values. The score of 6.31 is not arbitrarily chosen, but
the statistically calculated optimum for the best possible spam filter
rate with as few false positives as possible. If you increase the
value, more spam will get through; if you lower it, your false
positives will increase."
The comments about adjustments are true, but the idea that it is optimum
is flat-out nonsensical.
The key question is how you weight a false positive compared to a false
negative. Only after you decided that can you pick an optimium, for a
given corpus of already-received mail.
It may be that the value is outdated, but that is for the maintainers
of the relevant Debian package to decide. I'll just adapt my rules to
this one value.
That is an odd position. It is very easy to set the threshold in a
local config. Deciding instead to adjust scores to an oddball
threshold seems bizarre to me.
Personally, I don't use the 5, but instead have shades of grey, where
=1 is binned into mailboxes that are "maybe spam" through "very likely"
spam, and at some score, I reject at the MTA level.
I find that legit mail shows up in e.g. spam.2 (>= 2 and < 3), but it is
almost never mail that I would be upset to have missed (but I don't) or
mail that I would be upset to not get in a timely manner (I only see it
every day or so). However, this really drops the FN rate of spam in my
INBOX, which matters a lot to me. Basically I consider a FP into my
"spam.1" mailbox, as long as it isn't really important to me, to be not
a big deal at all, and I'd rather have 10 or those than 1 FN in my
INBOX. But, actually MTA-rejecting mail that I shouldn't, a FP at that
level, is a big deal, and I avoid it. I think it's about one message a
year -- and while it's ham, it's very spammy ham.
Methinks this is a perfect example of "one man's spam is another man's ham." Or
in my case, "A woman's spam is often a man's ham."
{^_-} <- hopelessly square and antiquarian by today's standards. e.g. the
XXXlist wars.
