is it any way to secure email service?

here is a popular security measure for email called "pgp" (pretty good
privacy) which uses a key service to encript emails.
Here is an explanation from http://www.keyserver.net/en/

To communicate securely with other users, each user will have to
create two complementary keys (also called a key pair) consisting of a
Private Key and a Public Key.
Your Private Key is confidential and only you have access to it.
Your Public Key, which is automatically generated from your Private
Key, as its name implies, is "public" and can be freely exchanged with
other users. To facilitate this key distribution, there are several
"Key Servers" on the Internet. Their purpose is to be a repository of
Public Keys. They contain hundreds of thousands - soon millions... -
of Public Keys belonging to people from all over the world. Once you
have created your own key pair, you may publish your Public Key on one
of these Key Servers. The Key Servers are regularly synchronized.

for more info see http://www.keyserver.net/en/