We are an email marketing company and we have our own sending platform - sending software, servers and dedicated IPs (we are RIPE member).
We usually reach the inbox with all ISPs but hotmail. We need someone to help us to improove our open rates in Hotmail.
P.S. We are using open source MTAs, we have dedicated IPs, DKIM, RDNS, feedback loops, whitelists, SNDS, bounce removing every 3 hours.