Can you please check that users get other notifications? In a group you only get notifications for pages if pages are shared with the group and "Shared page notifications" are ticked in the group settings.
Forum notifications are only made to users when they are subscribed to the forum. And people can unsubscribe from forums quite easily.
You should also check that the user hasn't set his notifications to appear only in the inbox if he's subscribed to a forum.
If no user gets any email notifications and your settings are correct, you should check your mail log and see if messages are sent out and you can also check your Mahara config.php file and see if all messages actually are re-routed to one specific address. That is what we usually do for test systems just so that users aren't bothered by test mails.
Cheers
Kristina
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