I just happened to notice that there is a button/tickmark next to "Date/Time Sent", what does it do?

That is so you can check them and then choose delete. So you don't delete ones you want to keep, or you can forward them to other people. Nothing too special. But in order to either delete or forward you have to check at least one of the boxes.

Yes, of course I can select messages but there's a checkbox above messages, too, which doesn't seem to do anything. Is it just a bug?

I just looked at your screen shot. Are you refering to the box that doesn't have a date by it? It is supposed to select all when you check that. Possibly the browser you are using in *IX doesn't support that? Have you tried it with a different browser?

Yep, it's JavaScript, that's why it doesn't work in NetPositive. Thanks for answering

Code:

function CheckCheckAll() {
	var TotalBoxes = 0;
	var TotalOn = 0;
	for (var i=0;i<document.form.elements.length;i++) {
		var e = document.form.elements[i];
		if ((e.name != 'allbox') && (e.type=='checkbox')) {
			TotalBoxes++;
			if (e.checked) {
				TotalOn++;
			}
		}
	}
	if (TotalBoxes==TotalOn) {
		document.form.allbox.checked=true;
	} else {
		document.form.allbox.checked=false;
	}
}