gnus-exit-gnus-hook

gnus-exit-gnus-hook is a variable defined in `gnus-group.el'.
Its value is

(mm-temp-files-delete mm-destroy-postponed-undisplay-list)

Original value was

• This variable may be risky if used as a file-local variable.

Documentation:
Hook called when exiting Gnus.

You can customize this variable.