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.
opkg install fontconfig
fc-list, you will have to manually copy some fonts from any other Linux machine. Alternatively, download a set of fonts from here.
Important: Depending upon the configuration of your QNAP, the font files you manually copied to
get deleted by QNAP when the machine is rebooted. In that case, you will have to copy the font files again.