I'm assuming you are at least slightly familiar with classic ASP, so I will allow the comments in the code to provide the map for whats going on here.  The SendMail.ASP file uses CDONTs to send the email. Make sure your server supports CDONTS. Here's the ASP code:

<%
dim themail, thename, themessage, i

'Gets the incoming variables from flash
themail = Request("email_txt")
thesubject = Request("subject_txt")
themessage = Request("message_txt")

'Decalre and create email object
dim objmail

set objmail = Server.CreateObject("CDONTS.Newmail")
'error handler, if error encountered, ignore it and proceed
On Error resume next

'build the email using the variables from flash
objmail.From = themail
objmail.To = themail
objmail.Subject = thesubject
objmail.Body = themessage
objmail.Send
'error handler, if error encountered, ignore it and proceed
On Error resume next

'If any errors were encounter then run this code
If Err.Number <> 0 then
'tells flash ASP failed and terminates the ASP file.
Response.Write "&server_mes=fail"
Response.End 
else
'Send message back to flash saying everything was ok.
Response.Write "&server_mes=ok"
End if 

%>

Assuming your server supports CDONT's, then this script should work well. Let's move on.