EmailValidRegex.cs

using System;
using System.Text.RegularExpressions;

namespace Utils.Helpers
{
    public class EmailValidRegex : Regex
    {
        private const string Pattern =
            @"^(?("")("".+?(?<!\\)""@)|(([0-9a-z]((\.(?!\.))|[-!#\$%&'\*\+/=\?\^`\{\}\|~\w])*)(?<=[0-9a-z])@))" +
            @"(?(\[)(\[(\d{1,3}\.){3}\d{1,3}\])|(([0-9a-z][-0-9a-z]*[0-9a-z]*\.)+[a-z0-9][\-a-z0-9]{0,22}[a-z0-9]))$";

        public EmailValidRegex()
            : base(
                pattern: Pattern,
                options: RegexOptions.Compiled | RegexOptions.IgnoreCase,
                matchTimeout: TimeSpan.FromMilliseconds(250))
        {
        }
    }