When clicking the button in Firefox to create an email with a link of the current web page I get an error. The email button can be configured within the settings of Firefox (not about:config just the normal user gui settings).

This is the error message:

"The set mail program coudn't be started. Child process /usr/lib/x86_64-linux-gnu/xfce4/exo/exo-compose-mail couldn't be executed (file or directory not found)."

This worked previously but now on Xubuntu 20.04 64 bit beta it's not working anymore.

The program is located under /usr/share/xfce4/exo instead of /usr/lib/x86_64-linux-gnu/xfce4/exo. So creating a symlink worked:

sudo mkdir /usr/lib/x86_64-linux-gnu/xfce4/exo
sudo ln -s /usr/share/xfce4/exo/exo-compose-mail /usr/lib/x86_64-linux-gnu/xfce4/exo/exo-compose-mail