Here is the base of the code I use for my HTML email. I know you said you use CDOSYS, I use CDONTS. Not sure if it's possible for you to switch to CDONTS. This is in your inc_mail.asp (I'm sure it's something similar with CDOSYS http://support.microsoft.com/default.aspx?scid=kb;en-us;Q286431)
case "cdonts"
Set objNewMail = Server.CreateObject ("CDONTS.NewMail")
Dim HTML
HTML = "<!DOCTYPE HTML PUBLIC""-//IETF//DTD HTML//EN"">"
HTML = HTML & "<html>"
HTML = HTML & "<body>"
HTML = HTML & strMessage
HTML = HTML & "</body>"
HTML = HTML & "</html>"
objNewMail.From = strSender
objNewMail.To = strRecipients
objNewMail.Subject = strSubject
objNewMail.BodyFormat = 0
objNewMail.MailFormat = 0
objNewMail.Body = HTML
on error resume next '## Ignore Errors
objNewMail.Send
If Err <> 0 Then
Err_Msg = Err_Msg & "<li>Your request was not sent due to the following error: " & Err.Description & "</li>"
End if
on error resume next '## Ignore Errors