Probably making myself unpopular again. But this one-liner just adds the old ✉ envelope back.
Meanwhile I find the new activity popup more useful than the old /recent page. But I do like UI clutter, and still enjoy the retro look of the envelope. So here it is:
$("#hlinks .profile-triangle").prepend('<a href="/users/recent" class="envelope-off"></a> '); // ✉