But, Google has introduced a provision for making the entire GMail session through encrypted channel, so that no one in the network can analyze and interpret the mails being shown to the user. This is in fact a great feature of GMail, which make sure that your private, personal and intimate mails are not being read by a man in the middle of the network. To be specifically your boss or network administrator.
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In order to make the entire GMail session encrypted, just go the settings page of GMail and scroll to bottom of the General tab and in the Browser connection section select Always use https. And do not forget to click Save Changes button. Done, all your GMail communications are secured.
Also refer the article on basic computer security, if you are interested.