Exception "The SMTP host was not specified" where I'm using SpecifiedPickupDirectory in unit tests

I have in my controller action (I removet try/catch block for more clear code):

   [HttpPost]
    public ActionResult SendMessage(ContactViewModel model)
    {          
        if (ModelState.IsValid)
        {

                MailMessage message = new MailMessage();

                var administrator = new MailAddress("xxxx@gmail.com");
                var customer = new MailAddress(model.Email, model.Name);

                message.Bcc.Add(customer);
                message.Bcc.Add(administrator);
                message.Subject = "Message Subject";
                message.Body = model.Message;

                SmtpClient client = new SmtpClient();                    
                client.Send(message);

        }

        return PartialView("_ContactPartial", model);
    }

The action works correctly, the info about host are in web.config.

I want create unit test's for this action. I created in my project with test web.config:

<configuration>
  <system.net>
    <mailSettings>
      <smtp deliveryMethod="SpecifiedPickupDirectory">
        <specifiedPickupDirectory pickupDirectoryLocation="C:\MailTest\"/>        
      </smtp>
    </mailSettings>
  </system.net>
</configuration>

And there is basic unit test:

    [TestMethod]
    public void ContactControllerTest_SendMessage_PartialView()
    {
        //Arrange
        var controller = new ContactController();

        //Act
        var result = controller.SendMessage(contactViewModel) as PartialViewResult;

        //Asset
        Assert.AreEqual("_ContactPartial", result.ViewName");
    }

In the line

Elmah.ErrorSignal.FromCurrentContext().Raise(ex); 

I have exception: The SMTP host was not specified. Why it need it if in my web.config I selected SpecifiedPickupDirectory as delivery method?