using System.Text.RegularExpressions;
public static void Main()
var s = Regex.Match("Qualquer mensamgem (blabla@blabla.com)", @"\(([^)]*)\)").Groups[1].Value;
string input = "Qualquer mensamgem (blabla@blabla.com)";
string output = input.Split('(', ')')[1];
Console.WriteLine(output);