problems by sending email with c# and web.config in a webserver Win 2003

Hi, this is my first time here, but I was looking for something that
may help me, and still, I haven't found something to use.

I'm using a website made in .NET with C#, when I'm running my site from
my PC, everything seems right, but when I publish the website, and send
it to my real website, everything works but the mail sending.

I have red some groups and topics, and everywhere I can found:
- Use the following syntax:
<system.net>
<mailSettings>
<smtp from="one_mail@xxxxxxxxxxxxxx">
<network
host="smtp.yourdomain.com"/>
</smtp>
</mailSettings>
</system.net>
- Or other with some modifications:
<system.net>
<mailSettings>
<smtp from="one_mail@xxxxxxxxxxxxxxx">
<network
host="smtp.yourdomain.com" userName="" password="" port="25"/>
</smtp>
</mailSettings>
</system.net>

Even without the port, it works on my PC, but in the real website, it
doesn't.

I'm not sure if something is missing, my local website is running on a
Windows XP professional edition, with .NET Framework 2.0, and the
website is on a Windows 2003 Server, with the .NET client installed.

Somewhere I red that .NET uses proxy configuration from IE, and I can
use IE in the webserver, but it does not use any proxy.

Also, I can send emails in other way, and THAT way is working anyway,
but this mail settings in the web.config file are showing an error
message.

I tried allowing the port in the firewall, but still nothing.

My questions are:

- Can I have this settings on this file working properly by doing
something in the server, or in the website?
- How can I check the commands sent by my website? Maybe if I can see
the real message, I can figure out a way to make it "recognized". (see
the error mesage below)
- Or, otherwise, can I avoid the mail settings in web.config? Because
when I tried to "avoid its use", by deleting the system.net section,
the website, in my PC, shows a message telling me that this section is
needed.


The error message obtained from the real website is the following:

Error: System.Net.Mail.SmtpException: Syntax error, command
unrecognized. The server response was: Unauthorized relay msg rejected
at System.Net.Mail.RecipientCommand.CheckResponse(SmtpStatusCode
statusCode, String response)
at System.Net.Mail.SmtpTransport.SendMail(MailAddress sender,
MailAddressCollection recipients, String deliveryNotify,
SmtpFailedRecipientException& exception)
at System.Net.Mail.SmtpClient.Send(MailMessage message)
at System.Web.UI.WebControls.LoginUtil.SendPasswordMail(String
email, String userName, String password, MailDefinition mailDefinition,
String defaultSubject, String defaultBody, OnSendingMailDelegate
onSendingMailDelegate, OnSendMailErrorDelegate onSendMailErrorDelegate,
Control owner)
at
System.Web.UI.WebControls.PasswordRecovery.AttemptSendPasswordUserNameView()
at System.Web.UI.WebControls.PasswordRecovery.AttemptSendPassword()
at System.Web.UI.WebControls.PasswordRecovery.OnBubbleEvent(Object
source, EventArgs e)
at System.Web.UI.Control.RaiseBubbleEvent(Object source, EventArgs
args)
at System.Web.UI.WebControls.Button.OnCommand(CommandEventArgs e)
at System.Web.UI.WebControls.Button.RaisePostBackEvent(String
eventArgument)
at
System.Web.UI.WebControls.Button.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent(String
eventArgument)
at System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler
sourceControl, String eventArgument)
at System.Web.UI.Page.RaisePostBackEvent(NameValueCollection
postData)
at System.Web.UI.Page.ProcessRequestMain(Boolean
includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)


By the way, sorry for misspellings, I'm not "english borned".

Thanks for your time, any suggestion or answer is welcome.

.