[Dovecot] Antispam plugin / sa-learn

Mathieu R. mathieu at 400iso.net
Fri Sep 13 19:06:38 EEST 2013

Le 13/09/2013 17:29, RW a écrit :
> On Thu, 12 Sep 2013 22:09:42 +0200
> Mathieu R. wrote:
>> 22:01 root at effraie01 ~ # sa-learn --username=vmail --backup
>> v       3       db_version # this must be the first line!!!
>> v       0       num_spam
>> v       0       num_nonspam
> sa-learn --username sets the virtual user not the unix user.  (BTW
> sa-learn --dump magic is a quicker way of reading the metadata)
> By default SA stores the bayes database files under a user's home
> directory. If you run sa-learn as vmail, which doesn't have a home
> directory, it will probably just give up.
> What you need to do is set bayes_path (in local.cf) to a directory to
> which vmail has access, then run sa-learn as vmail. Alternately you 
> can
> setup one of the SQL backends.

Setting bayes_path made it fall in work, thank a lot!

> I'm posting this through gmane as I'm not subscribed to dovecot list. 
> I
> replied in that SpamAssassin list before spotting that it was
> cross-posted. You can ignore most of it now, but I'll quote what I
> wrote about learning ham:
>  "I'm sceptical that the Antispam plugin can learn enough ham this 
> way.
>   As I understand it the only mail that gets learnt as ham will be
>   false-positives based on the overall spamassassin score, 
> irrespective
>   of the Bayes result. Bayes needs (by default) 200 spams and hams to
>   even start classifying and much more for optimal results - I don't
>   expect to get 200 FPs in the rest of my life. Unless this is high
>   volume server with a shared database, I'd suggest either learning a
>   few thousand hams manually, or implementing an unsure folder. You 
> can
>   also mitigate the problem by autotraining with a high ham 
> threshold,
>   but then you really need to be careful to move all spam to the spam
>   folder. "

as my english is approximative, i'm not sure to really understand what 
you mean :

should i :

  - do not use antispam-plugin to learn spam, but do it manually with 
sa-learn /path/to/ham ?
  - do not use antispam-plugin at alla ?
  - use antispam-plugin to learn ham, but still do it by hand with  
sa-learn /path/to/ham ?
  - take care for something else ?

Mathieu R.

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