Connection Refused Error When Sending Email

I feel silly asking because it's been asked so many times before, but I just can't figure out what's up. I get the "No connection could be made because the target machine actively refused it 127.0.0.1:25" error when trying to send email through the site. I took my code fresh off of the sample page: https://my.discountasp.net/web-manager/iis7-recycleapp.aspx

Relevant Web.config settings:

Code:

    <system.net>
        <mailSettings>
            <smtp>
                <network host="localhost" port="25" />
            </smtp>
        </mailSettings>
    </system.net>

Here's the full stack trace:

Code:

[SocketException (0x274d): No connection could be made because the target machine actively refused it 127.0.0.1:25]
   System.Net.Sockets.Socket.DoConnect(EndPoint endPointSnapshot, SocketAddress socketAddress) +239
   System.Net.Sockets.Socket.InternalConnect(EndPoint remoteEP) +35
   System.Net.ServicePoint.ConnectSocketInternal(Boolean connectFailure, Socket s4, Socket s6, Socket& socket, IPAddress& address, ConnectSocketState state, IAsyncResult asyncResult, Int32 timeout, Exception& exception) +224

[WebException: Unable to connect to the remote server]
   System.Net.ServicePoint.GetConnection(PooledStream PooledStream, Object owner, Boolean async, IPAddress& address, Socket& abortSocket, Socket& abortSocket6, Int32 timeout) +5482743
   System.Net.PooledStream.Activate(Object owningObject, Boolean async, Int32 timeout, GeneralAsyncDelegate asyncCallback) +202
   System.Net.PooledStream.Activate(Object owningObject, GeneralAsyncDelegate asyncCallback) +21
   System.Net.ConnectionPool.GetConnection(Object owningObject, GeneralAsyncDelegate asyncCallback, Int32 creationTimeout) +332
   System.Net.Mail.SmtpConnection.GetConnection(String host, Int32 port) +160
   System.Net.Mail.SmtpTransport.GetConnection(String host, Int32 port) +159
   System.Net.Mail.SmtpClient.GetConnection() +35
   System.Net.Mail.SmtpClient.Send(MailMessage message) +1213

[SmtpException: Failure sending mail.]
   System.Net.Mail.SmtpClient.Send(MailMessage message) +1531
   AdvancedCapitalGroup.contact_default2.Page_Load(Object sender, EventArgs e) in D:\Documents\AdvancedCapitalGroup\AdvancedCapitalGroup\contactacg\default2.aspx.vb:17
   System.Web.UI.Control.OnLoad(EventArgs e) +99
   System.Web.UI.Control.LoadRecursive() +50
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +627

What am I missing here? I'm sure it's a facepalm situation. All ideas appreciated.

Thanks,
Adam