Our email service actually detect by IP address, mean if the sender IP address are blacklisted, it will goes in to spam section in our email.
Few week back i meet a sales person who sell email marketing, according to that fella, they have few IP which did not get black listed, and while send 1000 over news letter to the client with their server IP, it won goes in to spam...
According to that fella, there are few associate which collect all the spam IP address, some thing like spam dictionary/spam directory service, and all our email service obtain all the spam list from those associate. so called filtering...
this is what i get from that "sales" fella, dono he bluff me or not...
