Posted
This request came from a user whose form created a CSV file which needed to be emailed. The way to do it is to add an entry into the $form->files array that the Email action can then read in the same way as it can an uploaded file.
In a Custom Code action before the Email action add a code snippet like this:
<?php $form->files['my_file'] = array( 'name' => $my_file_name, 'original_name' => '', 'path' => $my_file_path.$my_file_name, 'size' => '', 'link' => str_replace(JPATH_SITE.DS, JURI::root(), $my_file_path.$my_file_name) ); ?>
Change the highlighted parts to match the needs of your form and file.
Then you can use my_file (or whatever you changed that to) in the Email action Attachments box.