I think I've found a BUG in ZoneAlarm's junk-mail filter:

The "ZoneAlarm Junk Mail" folder does not empty itself into the "Deleted Items" folder if the ZoneAlarm Options | Configure Preferences | Settings | Configure option is set to 1 day. If it is set to 2 days it works.

Since 1 day is the shortest time you are allowd to set I guess there is a limit check in hte filter that is coded incorrectly.

OR - Have I missed some setting somewhere?

If it indeed is a BUG, and someone at Zone Labs is monitoring/reading this:

When you fix this problem, PLEASE give us the option to have spam go directly into Outlook's "Deleted Items" folder from where we can have it deleted automatically when we exit Outlook. I understand the potential danger with doing this, but my previous spam filter (SpamBayes) has this option, and in the sevral years I've been using it I've never had to regret it. Make this an "advanced" option if you must, but I can assure you that for a substantial percentage of you users the "ZoneAlarm Junk Mail" folder doesn't REALLY add any functionality.

Im running:

XP Pro SP2
Outlook 2003
ZoneAlarm Security Suite 6.1.737.000

Operating System:Windows XP Pro
Product Name:ZoneAlarm Internet Security Suite