Re: [hosers-talk] greylisting

[Joel Uckelman <uckelman@xxxxxxxxx>]

Thus spake Joshua:
> 
> Joel Uckelman sez:
> >I've been thinking about setting up greylisting on charybdis. What that
> >means is that a database of remote email servers would be kept, and only
> >mail from known servers would be delivered immediately; all other mail
> >servers would be asked to try again later, and then any mail servers which
> >actually try again are added to the database. This is pretty effective
> >against spam because usually legitimate mail servers make a second attempt
> >to deliver (a few minutes to an hour later, usually), while spammers tend
> >not to try again with the same message.
> >
> >So, would it bother anyone if I set up greylisting on charybdis? (This is
> >likely to affect your real mail only if you routinely receive mail from
> >people who have never contacted you before which needs to be acted upon
> >within a few minutes of it being sent.)
> 
> what's the downside? some legitimate mail will be delivered more
> slowly; anything else? would any mail never be delivered? or would
> that only happen in cases where a legitimate sender for some reason
> never tried again, or got through again?

The response code that a greylisted server would see indicates temporary
unavailability; the relevant RFC requires that compliant mail servers
try to deliver again. Any mail server which doesn't try again is Broken.
I know of none in use today which behave like this, so the chances of
lost mail are nil.
 
> assuming there are no big problems with it i'm fine with it. i get
> a lot of my mail through my school account, filtered to a gmail account,
> and a bit more straight to gmail. i still get legitimate mail at ellipsis
> but i get so much spam not caught by bogofilter or whatever we're using
> that i usually spend a lot more time deleting missed spam than reading
> the little real mail i get.

I don't understand why bogofilter works near-optimally for me, but not for
anyone else. Have you been training it on misclassified mail?
 
-- 
J.
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