尝试使用C＃发送电子邮件时出错

Question

我对C＃有点陌生，我正尝试通过控制台应用程序发送电子邮件，这是我的代码：

        MailMessage mail = new MailMessage();

        String emailUsr = "admin@email.com";
        String emailPassword = "password";

        mail.From = new MailAddress(emailUsr);
        mail.To.Add("usremail@email.com");

        mail.Subject = "test";

        string body = "test";


        SmtpClient smtp = new SmtpClient()
        {
            Host = "express server"
            , Port = 25
            , UseDefaultCredentials = false
            , Credentials = new NetworkCredential(emailUsr , emailPassword)
            , EnableSsl = true
        };

        try
        {
            smtp.Send(mail);
        }
        catch(Exception ex)
        {
            Console.WriteLine(ex);
        }

Error displayed

我不知道我的代码或服务器配置是否有错误。