I found a workaround using the message archive - Immediate via email, so all emails (including attachments) will be found later in a mailbox.
This is a pain point here as well.
We want to quarantine the emails and provide an alert to the user. This can be done, but the information you can provide to the user is too limited (basically just header type info) and there is no way to include the original body text to assist the user in determining if the attachment was legitimate and needed.
The ability to forward the message with the dropped part, and also quarantine the original at the same time, would be very helpful.