There are so many factors involved that it becomes unreasonable quickly. Your main problem is going to be getting everyone to use it. If you converted 25% of t

There are so many factors involved that it becomes unreasonable quickly. Your main problem is going to be getting everyone to use it. If you converted 25% of the people using email today to an end to end encryption system it means that they can either only email anyone else in that 25% or anytime they send or receive an email from the other 75% it's not going to be encrypted the entire way.