2
You might also check that notifications are enabled in the user's profile:
Notification Method = "Email (use address in my profile)"
Default Notification Mode = "Notify me of all selected updates"
In XOOPS 2.2.x, the associated database columns are:
user_profile.notify_method = 2
user_profile.notify_mode = 0
In XOOPS 2.0.x, if I recall correctly, those two columns are in the users table, but otherwise they work the same way.