Hi Kevin,

Here are some spamples -- I've specifically chosen the ones that did NOT score 
enough through other means to get tagged, i.e., these are false negatives.  
Note that many of them have valid DKIM and hit no other markers.  (The spample 
will NOT pass DKIM because headers have been modified for anonymity.)  If you 
run them through NOW you'll probably find they hit Razor and Pyzor and various 
other things... but they clearly didn't at the time of receipt.  Most of them 
score 4.6 unless they manage to have enough Bayes "poison" to score lower.  
(And I STILL don't know how they keep hitting only BAYES_50...)

https://pastebin.com/BQH3JgWD
https://pastebin.com/nXtZtUdm
https://pastebin.com/tBQt1Raw
https://pastebin.com/wEGvcs73
https://pastebin.com/nuFJ48k0
https://pastebin.com/ykCuEPNQ
** This last one I received from two different servers within a minute of each 
other.  The first one got nailed by SPFBL so it got marked as spam, but only 
because the combo of SPFBL (2.2) and local BOGUS_MIME_VERSION (4.0) pushed it 
over threshold.  This spample, the second of the two, didn't get nailed because 
the relay wasn't in SPFBL, so BOGUS_MIME_VERSION wasn't enough by itself at a 
score of 4.0, although it WOULD have been enough at a score of 4.5.

I should also mention I've seen at least a few recent ones that hit 
Mailscanner's "Eudora long-MIME-boundary attack" rule.  I'm not including those 
as spamples since they got sanitized by MailScanner so aren't useful, but I 
figured it was worth mentioning.

My feeling is that BOGUS_MIME_VERSION is incredibly useful during the early 
hits of snowshoers, before the RBLs, URIBLs, and content hash DBs can catch up. 
 Since it would seem to be 100% spam and 0% ham, I think scoring it very highly 
(4+ points) would be both safe and useful -- it will help nix these early hits 
but won't hinder anything else.

From my experience and these spamples, where most of them are scoring 4.6 (with 
4.0 of that from BOGUS_MIME_VERSION), an optimal score would be in the range of 
4.5 to 4.9 ... that would push these 4.6s to 5.1 or higher.

I've got MANY other examples in the Junk folders on my server, and I would be 
happy to send them to you privately if needed.

Cheers.

--- Amir

On May 30, 2019, at 9:24 AM, Kevin A. McGrail <kmcgr...@apache.org> wrote:
> 
> Fair enough.  Happy to look at spamples but I've seen virtually nothing in 
> the wild for this.

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