[asp.net] How to configure SMTP settings in web.config

I'm trying to fix an email issue with an inherited website and don't have access to the code (i.e. just the compiled files). This site needs to be hosted on a new web server having a different SMTP server.

Upon decompiling bits of the code I can see emails are sent using method like below in code snippet and SMTP is set as smtpMail.SmtpServer="localhost" but my new webserver's SMTP server is "relay.tagadab.com" how can we possibly configure this in web.config so that localhost is taken as "relay.tagadab.com"

Imports Microsoft.VisualBasic, System.Web.Mail

Shared Sub SendMail(ByVal ToAdd, ByVal FromAdd, ByVal Message, ByVal Subject)

    Dim msgMail As New MailMessage()

    msgMail.To = ToAdd
    msgMail.From = FromAdd
    msgMail.Subject = Subject
    msgMail.Headers.Add("X-Mailer", "ASP.NET")

    msgMail.BodyFormat = MailFormat.Text
    msgMail.Body = Message
    'SmtpMail.SmtpServer = "mail.the-radiator.com"
    SmtpMail.SmtpServer = "localhost"
    SmtpMail.Send(msgMail)

End Sub

I added this section in my web.config but that does not make a difference

<system.net>
    <mailSettings>
        <smtp>
            <network host="relay.tagadab.com" port="25" />
        </smtp>
     </mailSettings>
</system.net>

I don't have enough rep to answer ClintEastwood, and the accepted answer is correct for the Web.config file. Adding this in for code difference.

When your mailSettings are set on Web.config, you don't need to do anything other than new up your SmtpClient and .Send. It finds the connection itself without needing to be referenced. You would change your C# from this:

SmtpClient smtpClient = new SmtpClient("smtp.sender.you", Convert.ToInt32(587));
System.Net.NetworkCredential credentials = new System.Net.NetworkCredential("username", "password");
smtpClient.Credentials = credentials;
smtpClient.Send(msgMail);  

To this:

SmtpClient smtpClient = new SmtpClient();
smtpClient.Send(msgMail);

Web.Config file:

<configuration>
 <system.net>
        <mailSettings>
            <smtp from="[email protected]">
                <network host="smtp.gmail.com" 
                 port="587" 
                 userName="[email protected]" 
                 password="yourpassword" 
                 enableSsl="true"/>
            </smtp>
        </mailSettings>
</system.net>
</configuration>

Set IIS to forward your mail to the remote server. The specifics vary greatly depending on the version of IIS. For IIS 7.5:

1. Open IIS Manager
2. Connect to your server if needed
3. Select the server node; you should see an SMTP option on the right in the ASP.NET section
4. Double-click the SMTP icon.
5. Select the "Deliver e-mail to SMTP server" option and enter your server name, credentials, etc.