Sini Ruohomaa posted a comment on discussion Enigmail Support

Sorry about non-analytic bug reportingsortof post. I restored my ancient Sourceforge account for this purpose since these seem to be Big Issues but I don't have the capacity to track this down enough to make proper bug reports of everything. Background: I accidentally had a self-updating Enigmail installed as a plugin to Thunderbird 52.7.0 64-bit with the newer functionality AND an older one as an Ubuntu package (2:1.9.9-0ubuntu0.16.04). So some of this behaviour may only appear in a conflict of...