Mail aus Script ASP Script wird nicht verschickt.

Hallo Leute,
also mein Kollege hat ein ASP Script auf meinem Windows Server, dieses Script sollen einfach nur ein Formular senden, nun meldet der Server allerdings ne Fehlermeldung mit der ich nicht umgehen kann.

Server Error in '/' Application.

Transaction failed. The server response was: 5.7.1 <test@arcor.de>: Recipient address rejected: Access denied
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.Net.Mail.SmtpException: Transaction failed. The server response was: 5.7.1 <test@arcor.de>: Recipient address rejected: Access denied

Source Error:

An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.

Stack Trace:


[SmtpException: Transaction failed. The server response was: 5.7.1 <test@arcor.de>: Recipient address rejected: Access denied]
System.Net.Mail.RecipientCommand.CheckResponse(SmtpStatusCode statusCode, String response) +296
System.Net.Mail.SmtpTransport.SendMail(MailAddress sender, MailAddressCollection recipients, String deliveryNotify, SmtpFailedRecipientException& exception) +320
System.Net.Mail.SmtpClient.Send(MailMessage message) +2612
_Default.btnsend_Click(Object sender, EventArgs e) +371
System.Web.UI.WebControls.Button.OnClick(EventArgs e) +123
System.Web.UI.WebControls.Button.RaisePostBackEvent(String eventArgument) +140
System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument) +39
System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +3091


Version Information: Microsoft .NET Framework Version:2.0.50727.42; ASP.NET Version:2.0.50727.42


Weiß jemand rat, was ich hier machen kann ?
Die zugangsdaten im Script sind richtig.

W2k3 Server, bei S4Y

Gruß
Björn