In asp, universal email gets the server path for you, so it is not necessary to use the serverDirectory binding.
change:
set WA_MailObject = WAUE_AddAttachment(WA_MailObject,"" & cStr( Server.MapPath(WA_DFP_UploadStatus.Item("WA_Upload Result1").serverDirectory) ) & "/" & cStr( Server.MapPath(WA_DFP_UploadStatus.Item("WA_Upload Result1").serverFileName) ) & "")
to:
set WA_MailObject = WAUE_AddAttachment(WA_MailObject,"" & cStr( Server.MapPath(WA_DFP_UploadStatus.Item("WA_Upload Result1").serverFileName) ) & "")