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high false positive with Gmail

Bill Bogstad wrote:
> I've been seeing this with Gmail for a LONG time.  For me, it always 
> seems to be email that came via a mailing list.

As I noted, all the messages in questions were sent via mailing lists.

I guess this makes sense, given the system Gmail uses, as described in 
their anti-spam research paper[1].

Due to the way mailing lists redistribute messages, there generally 
won't be an association between the machine sending the message to Gmail 
and the author of the message, so Gmail classifies the message as 
unauthenticated, and subjects it to statistical filtering. (I'm 
speculating on the last bit, as the research paper didn't specify what 
they did with unauthenticated messages.)

Although I assume they authenticate the SMTP sender address, not the 
address in the message itself, and for a typical mailing list the SMTP 
sender address should be something that can be authenticated against the 
sending machine. So this still leaves me puzzled why it has problems 
with mailing lists.

1. A link to the paper and my summary of it appears here:

> I should note that my email is forwarded to Gmail from so
> Google's servers always see servers as the previous hop.

That's definitely problematic. As I recall, they strongly encourage 
users to spam filter mail before forwarding it.

If you didn't want Gmail to spam filter the forwarded messages (and it 
sounds like you do), you could change the way they get forwarded such 
that the SMTP envelope carried your address. Then you should 
be able to whitelist that.

> I just cleaned out my Spam box on Gmail and there were over 100 
> messages that were incorrectly marked as spam all from the same
> mailing lists which I have religiously marked as non-spam for
> over a year now. 

If those messages are not only from a mailing list, but also being 
forwarded through your account, then that's understandable.

When you whitelist a sender, you're whitelisting the author of the 
message (or more likely the SMTP sender), not the sending machine. And 
in order for that whitelist to apply, the sender needs to be 
authenticated, which won't happen in the cases of forwarded messages.

I'll keep an eye on my spam folder over the next few months and see if 
the situation improves now that I've provided feedback into the system. 
If it doesn't, I'll look into the headers and see why Gmail isn't 
authenticating the senders.


Tom Metro
Venture Logic, Newton, MA, USA
"Enterprise solutions through open source."
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