Re: Is running spamassin on a home server a waste? (was ... Re: TCP/IP over Bluetooth)
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On Wed, Apr 27, 2016 at 09:53:31AM +0100, Brian wrote:
> On Wed 27 Apr 2016 at 20:31:17 +1200, email@example.com wrote:
> > On Sat, Apr 23, 2016 at 12:57:08PM -0500, John Hasler wrote:
> > > > Thanks for making me think of that and the fact that over the last 10
> > > > years, the only ham its seen are its mistakes. So this question might
> > > > have had the seeds of something to help. :)
> > >
> > > My scripts copy all new non-spam to a ham directory which is fed to
> > > sa-learn every night and then the contents of both the ham and the
> > > spam directories are deleted.
> > IIRC, it seems pointless feeding your mail through a spam filter
> > if you're downloading it from your ISP/email provider.
> I think you are assuming the ISP provides a spam filtering service and
> you are happy to entrust the deletion of your mail to it.
There is still some truth to the above:
The most effective measure against spam these days is rejecting
the mail up front (i.e. while the SMTP session is active). This
way a (hopefully rare!) false positive is rejected in a way the
sender can act on it.
Once you got the mail it's too late. Either you have to generate
a bounce (not a good idea these days, because real spam will have
bogus headers and the bounce will hit a poor unsuspecting victim),
or you have to look into the spam anyway, or the spam disappears
in a black hole (again not a good idea, since in the false
positive case the sender will newer know).
Therefore once your ISP has accepted the mail for you it's kinda
"too late" -- they better have a good spam filtering setup in
which you have some influence (the spam filter will only work
if it has a notion of what *you* consider to be spam/ham).
- -- t
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