Troubleshooting End-To-End Encryption on QNAP

When running Xeams on QNAP, the End-To-End encryption runs into a problem and displays the following message in the Xeams.log:

A message without encryption was rejected due to content sensitivity. Cannot find any 
	fonts installed on the system

The End-To-End encryption feature creates a PDF file, which needs fonts installed on the machine. Fonts are installed by default on machines with GUI environments, such as Windows, Mac, or X-Windows on Linux.

Since almost everything you do on QNAP is through a web browser, font libraries are NOT installed on a QNAP machine by default. Unfortunately, installing these font libraries on QNAP require some manual work. Use the following steps to install fonts.

• Refer to this page to first install Entware-ng on QNAP.
• Then, run the following command to install fontconfig
  opkg install fontconfig
• Once fontconfig is installed, you should be able to run the following command to list available fonts.
  fc-list
• If you don't see any results returned by fc-list, you will have to manually copy some fonts from any other Linux machine. Alternatively, download a set of fonts from here.
  
  These fonts should go in /usr/share/fonts/truetype folder.
  
  
• Once done, restart Xeams

Important: Depending upon the configuration of your QNAP, the font files you manually copied to /usr/share/fonts/truetype may get deleted by QNAP when the machine is rebooted. In that case, you will have to copy the font files again.