There was a problem in the last few days but the administrator has fixed it, it should get back to normal soon.
Note that I had similar problems in the past but these were caused from my mail provider and not the forum, the email was send from the forum but was received late from my provided.
This can be checked if you compare the send-receive time, if the problem is caused by the forum then the late email should have the same send receive timestamps which means that it was send late but received immediately.
On the other hand if you see a send timestamp that is hours before you receive the email then it is your provider fault.
Here is how my send-received looked in this case that was the forum fault
Me too, I haven't received any post notification in the last 15 hours.
This was supposed to be fixed yesterday but I think it is getting worse, I have already contacted the administrator.