Created Unassigned: Crashes when using credentials [9627]

var sc = new SmtpClient {
Host = "localhost",
UseDefaultCredentials = true,
Credentials = new NetworkCredential("whatever", "andMorewhatevers"),
Port = 25,
EnableSsl = true
};
var mail = new MailMessage("tester@me.com", "testee@me.com") {
Subject = "My subject",
Body = "My body"
};

sc.Send(mail);

this crashes latest smtp4dev with an ArgumentNullException