Why do internet filters not work?????

The most annoying spam (Candy.., Simplisafe) need to filtered at the Cox email server level. Both the sender name and email address of the sender are changed in every email. They are spoofing their address and changing names and subjects to evade user filtering. Filtering needs to be done at the system level, looking at the actual domain(s) that are the source. However since the company that Cox outsourced their email system to doesn't seem to do system level filtering, we users are stuck with a spammed system, and perhaps the slowest email system that exists today.