im trying to register on a site and keep getting this message : Server Error

in '/' Application help anyone? im trying to set up a log in account on stoke colleges site to apply for a job,after entering my name,address,email details,i click next and get the following message:

Server Error in '/' Application.
Mailbox unavailable. The server response was: 5.7.1 Unable to relay for [email protected]
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.SmtpFailedRecipientException: Mailbox unavailable. The server response was: 5.7.1 Unable to relay for [email protected]

Source Error:

Line 1046: if (HttpContext.Current != null)
Line 1047: {
Line 1048: throw e;
Line 1049: }
Line 1050: }


Source File: e:\Inetpub\jobs.stokecoll.ac.uk\htdocs_2009-01-12\App_Code\CORE\EmailTracking.cs Line: 1048


any ideas and an easy step by step guide to overcome this?i have read forums but they make no sence to me lol,please help someone.......................