It can, but we had something which worked, then stopped. The meatbags are having a gumblefest.
(And… we need to fix a dormant account issue leftover from our import before we turn email summary on. I tried that on Wednesday and it caused a bit of an email storm… On the plus side, it did motivate a few dormant users to reactivate their accounts, but it did so by showing them the 23000 conversations they had missed since we went live.)