The file:// link was available inside of Evolution, but is now considered an exploit and not really used in browsers anymore. We wanted to replace the functionality however, so I found a solution and it's being tested. I created a new MIME type for files that end with '.lnk" inside of Firefox. Inside of this file is the path to a file located internally. The user is then able to open these linked/shared files without physically sending a copy. This too is very quota friendly.
When users double-click on the file, the normal MIME UI appears. The option circled in green is "Share Via Zimbra"
Using the same UI that was used to solve the LibreOffice temp file issue (described two blogs ago), a link symbol appears. User drags this into their composer window and a .lnk file is attached.
The recipient then clicks on the .lnk file and a box appears alerting them that a file has been shared, and then once opened the appropriate helper application (Evince, Acrobat Reader, LibreOffice, EOG, GIMP) opens based on the file type. I also have circled the new MIME type as it appears in Firefox.