The major feature of email, federation, is also it's biggest weakness. Rhese days, most emails travel between Microsoft, Gmail, Yahoo, and a few others, and th

The major feature of email, federation, is also it's biggest weakness. Rhese days, most emails travel between Microsoft, Gmail, Yahoo, and a few others, and they are in an arms race with spammers. Smaller providers have increasingly trouble keeping up with that fight and with the measures of the big providers because they can be out of business quite quickly if they relay spam and the major providers stop trusting them. Monopolization is also happening in that space.