I am trying to connect my server from .NET 6.0, but it takes a long time, and after that, it just won’t connect!

Here is my code :

using var smtp = new SmtpClient();
smtp.Connect("mail.uri.com", 25, SecureSocketOptions.StartTls);
smtp.Authenticate("username", "password");
smtp.Send(email);
smtp.Disconnect(true);

It gets stuck at first line (smtp.Connect) and won’t go further.

I expected to link to the server and send an email to the target ’email’, but it gets stuck at smtp.Connect