Email is simple, and works. I doubt anything is going to replace it as the default for what you list unless something massive and bizarre happens that brings down email in general so that everyone has to start from scratch and may as well put together something else.<p>Blockchain-based systems are... not simple, though they do do work. The advantage there is... what? The ability to verify sender/recipient? At the cost of massive power consumption to keep the encryption going, an unnecessary level of distribution for most purposes, and, as best as I can tell, the inability to delete anything that nobody involved cares about anymore.<p>If anything replaces email, it'll be basically email with security built in (end-to-end encryption and the guarantee that the From address matches the sender). More than that (maybe a little extra, I might have missed something) is overkill. Even that much is unlikely to come up except as patches on a per-provider basis, which might hopefully become omnipresent enough to remove support for the old version.
The biggest problem of using a blockchain for email is that you will need to have a copy of the blockchain to record all the transactions (mesages) sent in the past.<p>If you do this in the European Union, you are shooting yourself in the foot.<p>Why?<p>First because data protection laws dictate anyone can oppose against the treatment of his/her data in your systems.
Email is considered personal information here.
If you put email in a blockchain you cannot effectively remove data from it because it breaks the whole chain of signatures.<p>Maybe you could do something like cyphering the data before dumping it in the blockchain, and using a smart contract or inserting a special record to make it unavailable (not erased, but made not accessible).<p>Second, you cannot distribute / share personal data as you want. In some countries -like Spain- you need a signed autorization by the Director of the Data Protection Agency.
I just started the Free Data Foundation. The goal of the project is to support OSS that can replace "free" services that subsist on our data. Interestingly enough the maiden project is tentatively called Tmail (short for torrent mail).<p>It works somewhat like TOR in that it will depend on volunteers to host nodes that will communicate with existing email providers (outlook, gmail, yahoo, etc). The reason we need these nodes is that it's practically impossible to host an email server at a residential location because ISP's block port 25. Also most people don't have the desire or knowledge to maintain an email server.<p>Users can host their own delivery nodes (which will be plug and play software pre-installed on RPi's). These nodes communicate with the volunteer's host nodes over 80, thereby bypassing the ISP block of port 25.<p>There will also be an option for people hosting delivery nodes to share their resource with people who can't/won't host their own nodes which will allow people to sign up for email accounts without running their own software (a la gmail).<p>It gets way deeper than that, but I'll leave it there. You can follow the project at <a href="https://github.com/freedatafound/" rel="nofollow">https://github.com/freedatafound/</a>. I've also bought <a href="http://freedatafoundation.org" rel="nofollow">http://freedatafoundation.org</a> but there's currently nothing there.