The sent message will appear as Spam, with the name of who you to want. Ray Kurzweil is often quoted on this topic. Joo can send a message the Maria with the name of its Mateus friend, thus, when Maria to open the message goes to think that it was Mateus quemmandou. Additional information is available at kevin ulrich. But in the Linux, later I rank an article on the Windows.Logue as super user or place sudo before comandos1-Open the terminal and activate the mail:/etc/init.d/sendmail2-Abra server the terminal telnet that is in door 25: 253-Agora telnet localhost you can interact with the server, following the stages: MAIN FROM: RCPT YOU: DATE: oi pretty, as vc you? (.)The first line wants to say that you write the address of email that will want, exactly that you you are not Mateus.A second line you are a real address, of that person who you want to send the message; Third it wants to say message, is alone to type the text below; It finishes with a point between parentheses.