Hello Thom,

The object in ASP.NET cache cannot be used as actual file for amail
attachment. I think Manohar's suggestion is the right way to resolve the
problem. You can take a look at following code in the sample he recommended:

MailAttachment a = o as MailAttachment;
byte[] binaryData;
if(a!=null)
{
FileInfo f = new FileInfo(a.Filename);
sb.Append("--unique-boundary-1\r\n");
sb.Append("Content-Type: application/octet-stream; file=" + f.Name +
"\r\n");
sb.Append("Content-Transfer-Encoding: base64\r\n");
sb.Append("Content-Disposition: attachment; filename=" + f.Name + "\r\n");
sb.Append("\r\n");
FileStream fs = f.OpenRead();
binaryData = new Byte[fs.Length];
long bytesRead = fs.Read(binaryData, 0, (int)fs.Length);
fs.Close();
string base64String = System.Convert.ToBase64String(binaryData,
0,binaryData.Length);

..

Above code add an attachment to the mail and data is in the byte array.
Based on the sample, you can load your data in a byte array or stream, and
then add to the mail.

Luke