show Envelope-From and Reply-To as a mouse-over message on the “From” field in Webapp
Our e-mail gateway appliance has the option to filter “Envelope-From” addresses in e-mail headers. So we can avoid external e-mail pretend to be internal - if the users would check the internet header fields of an e-mail. But our users see only free text field “from” - that still contains the internal e-mail addresses or user names.
A mouse-over message on the “from” in Webapp, that shows some more information (like Envelope-From, Reply-To) would make it a lot easier to verify the sender. Even if there is no gateway that filters Envelope-From, it would be possible to detect fake Reply-To.
This function should be easy to implement and would give Webapp an additional security advantage against Outlook.