using System;

using System.Text.RegularExpressions;

public class Program

{

    public static void Main()

    {

        string input = "yma02142001@trupanion.com_829562eb-64c4-433b-b1bc-712c16728844.com";

        Console.WriteLine("Current:>>>> ("+ input + ")"+  Isvalid(false, input));       

        Console.WriteLine("Proposed Fix:>>>> ("+ input + ")"+  Isvalid(true, input));

    }

    private static readonly Regex Pattern = new Regex(@"^((?>[a-zA-Z-_\d!#$%&'*+\-/=?^_`{|}~]+\x20*|""((?=[\x01-\x7f])[^""\\]|\\[\x01-\x7f])*""\x20*)*(?<angle><))?((?!\.)(?>\.?[a-zA-Z\d!#$%&'*+\-/=?^_`{|}~]+)+|""((?=[\x01-\x7f])[^""\\]|\\[\x01-\x7f])*"")@(((?!-)[a-zA-Z\d\-]+(?<!-)\.)+[a-zA-Z]{2,}|\[(((?(?<!\[)\.)(25[0-5]|2[0-4]\d|[01]?\d?\d)){4}|[a-zA-Z\d\-]*[a-zA-Z\d]:((?=[\x01-\x7f])[^\\\[\]]|\\[\x01-\x7f])+)\])(?(angle)>)$");

    private static readonly Regex Pattern_fix = new Regex(@"^((?>[a-zA-Z-_\d!#$%&'*+\-/=?^_`{|}~]+\x20*|""((?=[\x01-\x7f])[^""\\]|\\[\x01-\x7f])*""\x20*)*(?<angle><))?((?!\.)(?>\.?[a-zA-Z\d!#$%&'*+\-/=?^_`{|}~]+)+|""((?=[\x01-\x7f])[^""\\]|\\[\x01-\x7f])*"")@(((?!-)[a-zA-Z-_\d\-]+(?<!-)\.)+[a-zA-Z]{2,}|\[(((?(?<!\[)\.)(25[0-5]|2[0-4]\d|[01]?\d?\d)){4}|[a-zA-Z\d\-]*[a-zA-Z\d]:((?=[\x01-\x7f])[^\\\[\]]|\\[\x01-\x7f])+)\])(?(angle)>)$");

​

​

    public static string Isvalid(bool IsChange, string input)

    {

        bool val;

        val = IsChange ? Pattern_fix.IsMatch(input) : Pattern.IsMatch(input) ;

        return val ? " Email is valid" : " Email is Invalid";

    }

}