This is resolved in Debian package version 0.12.2-2, currently available in Debian Testing/Unstable and Ubuntu 19.04.
xubuntu@xubuntu-VirtualBox:~$ dpkg -S exo-compose-mail-1 libexo-helpers: /usr/share/xfce4/exo-1/exo-compose-mail-1
This is resolved in Debian package version 0.12.2-2, currently available in Debian Testing/Unstable and Ubuntu 19.04.
xubuntu@ xubuntu- VirtualBox: ~$ dpkg -S exo-compose-mail-1 xfce4/exo- 1/exo-compose- mail-1
libexo-helpers: /usr/share/