Hola Danther, he estao mirando el codigo y en validateEmail() yo quitaría lo de "validate country code" porque creo que se podría hacer directamente con la expresión regular.

En este sitio he visto también una expresión regular pero creo que es .net:

http://haacked.com/archive/2007/08/21/i-knew-how-to-validate-an-email-address-until-i.aspx

  string pattern = @"^(?!\.)(""([^""\r\\]|\\[""\r\\])*""|"+ @"([-a-z0-9!#$%&'*+/=?^_`{|}~]|(?<!\.)\.)*)(?<!\.)" + @"@[a-z0-9][\w\.-]*[a-z0-9]\.[a-z][a-z\.]*[a-z]$";

package expresionesregularesemail;
import java.util.regex.*;
import java.util.StringTokenizer;
 
public class Main {
public boolean validateEmail(String email){
    //Pattern p = Pattern.compile("[a-zA-Z0-9]+[.[a-zA-Z0-9_-]+]*@[a-zA-Z0-9_]+[.[a-zA-Z]+]+"); //original
    Pattern p = Pattern.compile("[a-zA-Z0-9]+[.[a-zA-Z0-9_-]+]*@[a-z0-9][\\w\\.-]*[a-z0-9]\\.[a-z][a-z\\.]*[a-z]$");
 
 
   //@"^(?!\.)(""([^""\r\\]|\\[""\r\\])*""|"+ @"([-a-z0-9!#$%&'*+/=?^_`{|}~]|(?<!\.)\.)*)(?<!\.)" + @"@[a-z0-9][\w\.-]*[a-z0-9]\.[a-z][a-z\.]*[a-z]$"
 
   // Match the given string with the pattern
   Matcher m = p.matcher(email);
   return m.matches();
}
    public static void main(String[] args) {
        Main miMain = new Main();
        System.out.println("*****************************validateEmail******************************************");
        System.out.println("email: "+"example@cs.uns.edu.ar "+miMain.validateEmail("example@cs.uns.edu.ar")); 
        System.out.println("email: "+"name-surname@computer_name.net_name.com "+miMain.validateEmail("name-surname@computer_name.net_name.com"));
        System.out.println("email: "+"!u@hotm@ail.co "+miMain.validateEmail("!u@hotm@ail.co"));
        System.out.println("email: "+"u@hotm@ail.co "+miMain.validateEmail("u@hotm@ail.co"));
        System.out.println("email: "+"u@hotmail.co "+miMain.validateEmail("u@hotmail.co"));
        System.out.println("email: "+"u@hotmail.c "+miMain.validateEmail("u@hotmail.c"));
        System.out.println("email: "+"!u@hotmail.cc "+miMain.validateEmail("!u@hotmail.cc"));
        System.out.println("email: "+"uu@hotmail.cc "+miMain.validateEmail("uu@hotmail.cc"));
        System.out.println("email: "+"@hotmail.cc "+miMain.validateEmail("@hotmail.cc"));
        System.out.println("email: "+".u@hotmail.cc "+miMain.validateEmail(".u@hotmail.cc"));
        System.out.println("email: "+"u.u@hotmail.cc "+miMain.validateEmail("u.u@hotmail.cc"));
        System.out.println("email: "+"u u@hotmail.cc "+miMain.validateEmail("u u@hotmail.cc"));
        System.out.println("email: "+"u@h.cc "+miMain.validateEmail("5u@h.cc"));
        System.out.println("email: "+"5u@h.cc "+miMain.validateEmail("5u@h.cc"));
        System.out.println("email: "+"5.cc "+miMain.validateEmail("5.cc"));
        System.out.println("email: "+"5@h.cc "+miMain.validateEmail("5@h.cc"));
        System.out.println("email: "+"5@h.cc.d "+miMain.validateEmail("5@h.cc.d"));
        System.out.println("email: "+"5@h.cc.dd "+miMain.validateEmail("5@h.cc.dd"));
        System.out.println("email: "+"5@h.c.dd "+miMain.validateEmail("5@h.c.dd"));
        System.out.println("email: "+"avf-@h.c.dd "+miMain.validateEmail("avf-@h.c.dd"));
        System.out.println("email: "+"a-vf@h.c.dd "+miMain.validateEmail("a-vf@h.c.dd"));
        System.out.println("email: "+"avf@h.c.dd "+miMain.validateEmail("avf@h.c.dd"));
        System.out.println("email: "+"-avf@h.c.dd "+miMain.validateEmail("-avf@h.c.dd"));
        System.out.println("email: "+"_avf@h.c.dd "+miMain.validateEmail("_avf@h.c.dd"));
        System.out.println("email: "+"a-_-_.-_b--d__-@h.c.dd "+miMain.validateEmail("a-_-_.-_b--d__-@h.c.dd"));
        System.out.println("email: "+"a_._-@h.c.dd "+miMain.validateEmail("a_._-@h.c.dd"));
        System.out.println("email: "+"a_.-@h.c.dd "+miMain.validateEmail("a_.-@h.c.dd"));
        System.out.println("email: "+"a.-@h.c.dd "+miMain.validateEmail("a.-@h.c.dd"));
 
    }
}