Package: thunderbird Version: 1:52.4.0-1 It seems, that apparmor prevents using an external editor with Thunderbird. With apparmor, no external editor starts, nor is there any warning or error message to the user. If I "aa-disable usr.bin.thunderbird", it works fine.
I assume, that Thunderbird must be allowed to execute external programs under /usr/bin/, so that /usr/bin/emacs or other user defined editors can be used.
