In theory the network should respect each IP address as if it is held by a separate entity, who should be judged as an individual and not as part of a group. I

In theory the network should respect each IP address as if it is held by a separate entity, who should be judged as an individual and not as part of a group. In practice, due to bad actors, almost all internet services will in fact discriminate against you if your neighbors are (or have been) assholes. Sometimes they even discriminate against your IP address because they have PTSD about a different address that looks like your address. What can we do? Not a lot. If the customers of MSFT don't care enough to complain that email is not being delivered to them, MSFT doesn't care either.