Filename format for Email to

When sending an eBook by email to Amazon, the attachment filename is used to construct the title. Presently Calibre formats the filename as Title - Author, resulting in Amazon including the Author name in the title. Now that Amazon is using the Author from the metadata again, this is no longer helpful.

I cannot find where to configure the filename used for attachments in the Email to feature. Changing the Saving to Disk save template has no effect on Email to's attachment filename.