using System.Text.RegularExpressions;
static void Main(string[] args)
Regex emailPattern = new Regex(@"^((\w+([-+.]\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*)\s*[;]{0,1}\s*)+$");
"five@hotmail.me; six@six.com"
foreach (string email in emails)
Console.WriteLine("{0} {1} a valid email address.", email,
emailPattern.IsMatch(email) ? "is" : "is not");