since the nodes (mobile wallets) are standalone and it is not necessary everyone know everything about every transaction.
The heart of network are mobile phones which acting as network nodes.
If you can please explain better how exactly are you using mobile phone wallets as ''nodes'' and emails, because this sounds to me like a privacy nightmare.
You say there is no central authority but most email providers are centralized and they track and read your email like gmail for example.
Sorry but I see lot of holes in your theoretical medium post.