Let's try... Nope! You cannot. However, .zip (zipped / compressed) files are an accepted file type amongst others. So you may try to compress an Excel file and attach that, here's a test: View attachment Test_for_Evolor.xls.zip (click to download) If you click Go Advanced > Manage Attachments > the File Upload Manager with open. Look in the upper right corner and you will see a blue "?", click on that to view all accepted file types for attachment. See pic below:
