C# - How To Get The SMTP Settings Automatically From Web.config

I noticed that we always just are like:

SmtpClient mSmtpClient = new SmtpClient();
// Send the mail message
mSmtpClient.Send(mMailMessage);

And the only place the credentials are set are in web.config:

<system.net>
<mailSettings>
<smtp>
<network host="xxx.xx.xxx.229" userName="xxxxxxxx" password="xxxxxxxx"/>
</smtp>
</mailSettings>
</system.net>

So my question is, how does it automagically get them out?