static void Main(string[] args)
        {
            var list = new List<string> {"bajs@mail.com", "bajs@mail.com", "bajs@mail.com", "baj2s@mai2l.com"};
            var blacklist = new List<string> { "asd@lol.se" };

            var emails = list.Select(email => new MailAddress(email)).ToList();
            var hosts = blacklist.Select(email => new MailAddress(email).Host).ToList();

            foreach (var email in emails.ToList())
            {
                if (hosts.Contains(email.Host))
                {
                    list.Remove(email.Address);
                }
            }
        }