Unless you use something like PGP (see google.com) then email is not secure. This is INTENTIONAL since all governments want to be able to listen and read what the citizens are saying to each other.
That topic is well worn but after years of thought about it, PGP is the answer. The author has been dragged through the courts and more which is interesting reading in itself.
Hope this helps you understand the depth of what you asked for.
one day i read pdf fire frome one website since i have been able to read or send a secure mail . i would like to how i can use yahoo, hotmail, gmail mails ect. securely