using System;
using System.Text.RegularExpressions;

public class Test
{
	public static void Main()
	{
		var input = "\"one@tw;,.'o\"@hotmail.com;\"some;thing\"@example.com;hello@world";
		var mm = Regex.Matches(input, "((?:[^@\"]+|\"[^\"]*\")@[^;]+)(?:;|$)");
		foreach (Match m in mm) {
			Console.WriteLine(m.Groups[1].Value);
		}
	}
}