SunilPaul wrote:
mail filtering at the MTA is a must to avoid congestion and overloading of
"downstream" servers ... large ISPs like AOL (where I was Internet Product
Manager) implement MTA-level filtering out of necessity: a significant portion
of their traffic (ranging 5-50%) is spam or spam-related (responses, etc)...
not that existing filtering is helping that much ... :)
Please, hold just there for a moment.
My opinion is that large ISP anti-spam issues are quite different from
UA-filtering. I think it will improve the discussion a lot if we can
agree on that.
If you think otherwise, try to imagine the potential admin nightmare of
having "downstream" mail account users being able to put individual
filtering rules into action at "upstream" mail relays. It gives a chilly
feeling ...
As far as IETF is concerned, it might not want to endorse such
scenarios.
I think Tim made it quite clear in what contexts SIEVE are being
designed to work in.
The key words are "at point of delivery". Which I want to extend to "as
directed by and in the name of" individual mail accounts. Well, before
you flame me I better add, at least this is one very precise context
among other not so precise.
I made a point several months ago on this list that having rules of
individual accounts applied earlier than this point was probably not
desirable for many reasons. Some persons argued otherwise. So, no
consensus on that I'm afraid.
Tomas