Email without the use of proper encryption is inherently insecure. The main reason why the majority is still not encrypting their emails is convenience, or a lack of thereof.
We have seen announcements and talks about new email services that try to change all that, but there has not been anything created yet that you can make use of.
Cassiopeia's BitMail is a free decentral end-to-end encrypted email client for the Windows operating system. The service uses a whole array of security protocols and technologies to protect the contents of emails and your identity while you are using the program.
Note: BitMail is Open Source, and requires an independent security audit that verifies the applications security.
When you first start the program -- an installation is not required -- you need to select a passphrase that you want to use for protection. Cipher, hash and key size are set to aes256, sha512 and 2048 by default, which you can modify. You can change the cipher to camellia256, serpent256 or twofish, the hash to tiger or whirlpool, and the RSA key size to up to 15360.
The creation of the key may take a moment, and you may notice the program freezing during that period. This should not be cause for concern, as it will recover from that eventually. It is highly recommended to select a large passphrase to make sure the mailbox is properly secured.
All that is left then is to activate the kernel, which the program suggests to do, to get started.
Once that is done, you either need to create a BitMail Server from within the program, or connect to an existing BitMail Server.
You find your public email and chat keys on the Connect to BitMail Server page in the program interface. Use it for sharing with others, so that they can contact you using the application.
The program itself supports email and chat, with chat being the easier service to setup. Once you have selected the passphrase and started the kernel, you can switch to the Developer IRC tab to connect to a chat network to chat with contacts using the same level of encryption and protection that the program uses for emails.
If you do not have access to a BitMail server, you need to create one. To do so, you need to select an IP address, port and other parameters for it. This means that your computer has to be online for the ability to connect to the server.
Emails can be stored in the P2P network for offline friends, so that they can access them when they come online next time, regardless of whether you are online as well or not.
Participants need to add contacts to the address book. They can either add BitMail users or IMAP users to it by copying their public keys or email addresses and names in the form fields on the address book tab.
BitMail, as secure and protected as it may be, is too complicated to use for the average user in its current state. What I mean by that is not only the creation of the account, which is fine by itself, but also the interface and how everything is handled.
Chat is the one thing that seems to work just fine, and if email would be as convenient to use as chat, it could have a future.
Since that is not the case unfortunately, it is likely that it will remain a niche product.