New mail notifications (by Evolution) suddenly stopped working

Immediately following one of the latest Ubuntu system updates¹, notifications about newly arrived mails stopped working. The corresponding plugin² is still enabled, and I'm not aware of having changed any related configuration. Just to make sure, I've also checked the accounts' settings³ – but couldn't find anything related here. Neither can it be the "global notification daemon", as notify-send "Test" "Dummy notification" brings up the notification as expected.

I'm out of ideas where else I could check (some notification service that needs to be started explicitly but somehow failed? Notifications for other apps like Skype still pop up, and notify-send works as expected). I've already checked syslog for errors, but none are shown.

I'm running Evolution 3.4.2-1ubuntu3.1~stracciatellappa+precise1 on 12.04 here. I've checked for the mail-notification-evolution package, it's not installed⁴ – but as notifications worked before the last reboot, this cannot be the reason.

In case it matters: I'm using LXDE as desktop environment, but Gnome desktop is installed as well (though not selected as default). Again, as it worked in the past (before that last update/reboot), all required components should be available.

Update: I've just figured evolution-indicator should be responsible for notifications here. But there were no changes to that package either within the last year.

Any ideas what I could check/adjust to make notifications from Evolution work again?

^{1: I'm not sure which update exactly it was (there were no updates for Evolution itself); the issue started after the latest reboot. I assume it were the last kernel updates (3.2.0-94), but cannot tell for sure. Walking through the list of latest updates/installs in /var/log/apt/history.log doesn't reveal anything I'd recognize as related.}

^{2: Edit › Plugins › Notifications for new mails}

^{3: Edit › Settings › (Account_Name)}

^{4: according to dpkg -l mail-notification-evolution it never has been installed – it doesn't even have an install candidate in the stracciatella PPA I've used to install Evolution 3.4.2 from quite some time ago; the package in the "standard repo" depends on Evolution < 3.3 and thus cannot be(en) used anyway}