Security is a funny thing. For it to work, you have to do it all the time. Wearing a seatbelt half the time isn’t a good strategy—wearing the seatbelt every time is.
Sending scanned images of inbound, daily mail via email attachments, or a “scan-to-email” method, was never intended to be a secure, permanent operation. This was only a temporary solution conjured up in response to the pandemic crisis.