using System;
using System.Text.RegularExpressions;

public class Test
{
	public static void Main()
	{
		string pattern = @"(?:To:\s+|\G(?!^))(?:,\s*)?([^\s@,]+@[^\s@,]+)";
        string input = @"To: sandy.lewis@test.com,alewis@testpage.com, drtmirk@test.org.au ,";
        RegexOptions options = RegexOptions.Multiline;
        
        foreach (Match m in Regex.Matches(input, pattern, options))
        {
            Console.WriteLine(m.Groups[1].Value);
        }
	}
}