Re: HELP!! spamassasssin killing my server

2008-06-16 Thread Matus UHLAR - fantomas
> Matus UHLAR - fantomas schrieb:
> >On 12.06.08 18:51, Matthias Leisi wrote:
> >>On the company mailserver, we take a very conservative approach, and 
> >>only Spamhaus SBL+XBL are used at the MTA level. 
> >
> >you should switch to ZEN in such case, SBL+XBL is obsolete now.

On 13.06.08 18:49, Matthias Leisi wrote:
> We use a local feed, so querying SBL and XBL separately is not an issue. 
> For some obscure non-technical reason, we can currently not switch to 
> anything else (nor do we really need to, since queries only run local).

When people use "sbl+xbl", I guess they mean "sbl-xbl.spamhaus.org"
blacklist. If you query them separately, it's something different of course.
However you are then missing PBL which is another part of zen.
-- 
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Re: HELP!! spamassasssin killing my server

2008-06-13 Thread Matthias Leisi


Matus UHLAR - fantomas schrieb:

On 12.06.08 18:51, Matthias Leisi wrote:
On the company mailserver, we take a very conservative approach, and 
only Spamhaus SBL+XBL are used at the MTA level. 


you should switch to ZEN in such case, SBL+XBL is obsolete now.


We use a local feed, so querying SBL and XBL separately is not an issue. 
For some obscure non-technical reason, we can currently not switch to 
anything else (nor do we really need to, since queries only run local).


-- Matthias


Re: HELP!! spamassasssin killing my server

2008-06-13 Thread Matus UHLAR - fantomas
On 12.06.08 18:51, Matthias Leisi wrote:
> On the company mailserver, we take a very conservative approach, and 
> only Spamhaus SBL+XBL are used at the MTA level. 

you should switch to ZEN in such case, SBL+XBL is obsolete now.

-- 
Matus UHLAR - fantomas, [EMAIL PROTECTED] ; http://www.fantomas.sk/
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"That's nothing. If you play it forward it will install Windows."


Re: HELP!! spamassasssin killing my server

2008-06-12 Thread Matthias Leisi


Rob McEwen schrieb:


http://www.dnsbl.com/2007/05/spamcop-bl-another-look-its-accurate.html

Therefore, when you said, "too many false positives", are you referring 
to FPs from *before* that transformation of SpamCop? Or, are these 
*recent* FPs, spotted after that transformation?


It's twofold:

On my private mailserver, there is some older (definitely pre-2007) 
history of FPs (and since then I only use it in SA context there).


On the company mailserver, we take a very conservative approach, and 
only Spamhaus SBL+XBL are used at the MTA level. I run a daily report 
similar to SAs own masscheck reports; there, I see quite an overlap 
between the Spamcop BL rule and eg local whitelisting rules (based on 
whitelist_from_rcvd, content-based whitelisting rule and [to a limited 
degree] RCVD_IN_DNSWL_NONE/_LOW rules).


Just to be very clear: I value the Spamcop BL very much, and it is very 
effective. However, it has a too high FP rate in my environment in order 
to safely use it on the MTA.


I'll see whether I can grab some extract of it tomorrow and post it here.

(Also, I'm not trying to argue... just trying to learn... and seeking 
clarity!)


Seconded :)

-- Matthias



Re: HELP!! spamassasssin killing my server

2008-06-12 Thread Rob McEwen

Matthias Leisi wrote:

Be careful with using the Spamcop blacklist to reject messages -- while it
is perfectly fine as a blacklist to use in a scoring scheme such as
SpamAssassin, I found it to have too many false positives to use it for
outright blocking.

If you use it for blocking, then you should consider complimenting your
setup with a whitelist _on the MTA level_.
  

Matthias,

At some point around spring of 2007, SpamCop made dramatic improvements 
with regards to FPs.


Al Iverson details this here:

http://www.dnsbl.com/2007/05/spamcop-bl-another-look-its-accurate.html

Therefore, when you said, "too many false positives", are you referring 
to FPs from *before* that transformation of SpamCop? Or, are these 
*recent* FPs, spotted after that transformation?


(Also, I'm not trying to argue... just trying to learn... and seeking 
clarity!)


Rob McEwen



Re: HELP!! spamassasssin killing my server

2008-06-12 Thread Matus UHLAR - fantomas
> > Consequently I disabled the checks. Now, using spamhaus.org and spamcop
> > the
> > overload has disappeared.

On 12.06.08 10:16, Matthias Leisi wrote:
> Be careful with using the Spamcop blacklist to reject messages -- while it
> is perfectly fine as a blacklist to use in a scoring scheme such as
> SpamAssassin, I found it to have too many false positives to use it for
> outright blocking.

otoh, SpamCop is probably the most effective in detecting spam outbreaks. It
only lists machines that spammed last 48 hours and it lists them very soon.

according to SpamCop, it's designed to used for temporary rejects (IIRC).
However I think this way people would get much of the spam, only later, when
the machine is not listed (but the spam may still be in the queue), even
without increased score (because the machine is not in the queue).

In such case we only can hope that the spam will be catched by DCC, RAZOR,
PYZOR, URIBL's and some others.

-- 
Matus UHLAR - fantomas, [EMAIL PROTECTED] ; http://www.fantomas.sk/
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Re: HELP!! spamassasssin killing my server

2008-06-12 Thread Matthias Leisi

> Consequently I disabled the checks. Now, using spamhaus.org and spamcop
> the
> overload has disappeared.

Be careful with using the Spamcop blacklist to reject messages -- while it
is perfectly fine as a blacklist to use in a scoring scheme such as
SpamAssassin, I found it to have too many false positives to use it for
outright blocking.

If you use it for blocking, then you should consider complimenting your
setup with a whitelist _on the MTA level_.

-- Matthias