I have noticed it on occasion (maybe 3 times so far) that I don't receive an email when I receive a new comment. This hasn't been on just one post or at the same time of day.
The email address I use is gmail and I've received comments notification before and after the comment.
It's also comments from different people.
All in all it's not such a big deal at the moment, as I knew who commented on those occasions, but I was wondering what the problem is?