Why is smtp email not being sent?

Question

ASP.NET

MailAddress from = new MailAddress("email", "name");
            MailAddress to = new MailAddress("email");
            MailMessage m = new MailMessage(from, to);
            m.Body = $"text";
            SmtpClient smtp = new SmtpClient("server", 25);
            smtp.UseDefaultCredentials = false;
            smtp.Credentials = new NetworkCredential("email", "password");
            smtp.EnableSsl = false;
            smtp.Send(m);

Email is not sent from the asp.net core application, throws a SocketException. The server is working and the data is correct (checked through the smtp tester)

Answer 1

checked with smtp tester

What works from one place may not work from another. With a simple "telnet server 25" try from the machine where the code is running.