Thunderbird: nsemail and nscopy files left in /tmp
This bug was introduced in v68.x and it is not yet fixed. After investigation here is the exact situation:
Bug detail:
Thunderbird do use ~/tmp/ns*
since earlier version when sending email, but it also do delete those temporary files just after using them, while tb is still open. On v68.x a coding mistake make thunderbird try to delete those temporary files on the location /tmp/ns...
instead of ~/tmp/ns...
thus setting $TMPDIR
variable to /tmp
fix the issue. (awaiting an upstream update)
Solution:
Using the following command to run Thunderbird will fix the issue (similar to the other answer)
export TMPDIR=/tmp; thunderbird;