What is missing in this Asp.Net Sub Procedure that gives error Message?

Please this Sub Procedure is intended to assist me  accept or reject an offer when i click on the Accept Offer and Reject Offer Buttons.
However, it gives an exception handling error messages on:  SMTPServer.Send(AnEmail)
SmtpException was unhandled by the user code. Mailbox unavailable. The server response was: 5.0.0 Spam rejected  
Please Sub Procedure code that  needs to be corrected before a user can accept or reject SwapList  from the listbox. Please i have been with this exception handling error for more than 3 weeks now, sop your help is needed.
Thanks
Auspackuk
 
Private Sub AcceptOffer(ByVal SwapNo As Integer, ByVal OfferNo As Integer) 'this sub accepst an offer made on a swap 'it accepts two parameters the swap number and the offer number 'it sends an ...