using System;

using System.Text.RegularExpressions;

public class Program

{

    public static void Main()

    {

        var s = Regex.Match("Qualquer mensamgem (blabla@blabla.com)", @"\(([^)]*)\)").Groups[1].Value;

        Console.WriteLine(s);

        string input = "Qualquer mensamgem (blabla@blabla.com)";

        string output = input.Split('(', ')')[1];

        Console.WriteLine(output);

    }

}