I noticed that at some point in the past day and a half, the comment system for my site has stopped sending email notifications. The notifications were working fine until at least mid-morning yesterday, but since then I've stopped getting any. If I try leaving a comment as a test, it shows up in the moderation queue as normal, but no notification.
The only thing that's changed since then was that the WP-Optimize plugin was updated to 1.8.6 very early this morning. Is it possible the latest version is somehow interfering with comment notifications? I'm not sure if there's anything in the latest plugin that calls or would conflict with the same function, but since it's the only change that preceded the problem, it seems an obvious suspect. I tried turning off the plugin (not uninstalling it) and leaving another test comment, but that didn't seem to make any difference.