[afnog] Spamassassin warning

[Kenneth Kabagambe]

An excellent alternative to spamassassin is dspam 
(http://www.nuclearelephant.com/projects/dspam/) whose
design addresses most of the issues Geert raises.

Geert Jan de Groot wrote:

>Hi guys,
>
>Just so you know, spamassassin has a nasty failure mode that
>you should be aware of:
>1. Spamassassin is reasonable CPU-intensive and hence makes a higher
>   load on your mailserver
>2. If the load peaks (for instance, because of a mail peak), the load
>   may rise high enough so that the MTA temporary doesn't accept mail
>   till the load drops a bit.
>   It takes a while for the peak to get through the filter system,
>   so the load stays a while
>3. During this time, at various places in the world mail gets queued
>   waiting for your MTA to accept mail again
>4. Once the load lowers and the MTA accepts mail, the additional mail
>   queued will raise the load again, which again causes the MTA to block.
>   All the mailservers together trample the mailserver as soon as it
>   accepts mail again, till it stops accepting mail.
>5. Point 3-4 happen over and over, oscillating between accepting
>   and not-accepting mail
>
>The places where I've seen this, the ISP had no choice but to 
>disable spamassassin for a while just to lower the floodgates.
>
>To me, this effect came as a surprize the first time I saw it,
>and I think you may want to be aware of it and at least monitor
>the load on your boxes.
>
>Hope this helps,
>
>Geert Jan
>
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