You can find all your notification settings right here
And if that link doesn't work for you, go to your profile, then look to the left. You'll see all these links to different parts of your profile; find "notifications" and click it.
Does that help?
As far as I know of, you can't make it to where you'll receive emails when you're offline but not
receive them when you're online. You'll have to personally adjust your settings when you get online and when you are about to get offline.