Delete prior sent mail
It's great that I can remove scanned incoming mail from your servers using the delete feature.
This is a request to provide a delete feature for mailed letters. When I upload a document for you to mail for me it ends up on your server forever, or for some long period, with no option to delete it.
Another option would be to delete the documents as a matter of course after printing and mailing. Obviously, the sender already has the document. Leaving only the document file name, not the entire document in the mailing record would be sufficient.