I personally could not care less if the architecture document
has the word "sieve" in its diagrams or not.
Same here. And there are no RFCs about "SAREs" or "procmail
recipes" I'm aware of.
I think you seriously underestimate the extent to which Sieve
is now used by large ISPs.
Among others my ISP (rather small in DE), but apparently also
my former ISP (T-Online) if my interpretation of one "Sieve"
mail header seen yesterday can be generalized. T-Online is
AFAIK one of the largest ISPs worldwide.
A lot of the time the fact that Sieve is being used is entirely
They use a "Sieve:" header field here. Not yet listed in the
header field registries, is it defined in one of the Sieve I-Ds ?