If you try to edit an Autoresponder Rule which has a start/end time set, you may notice that you can't edit the dates in there.

This is because VPOP3 prevents you from setting it so that the “start date” is after the “end date”, so dates after the end date will be disabled in the “start date” date picker, and vice versa. So, if you are changing the dates to later dates than they were, you will have to change the “end date” first, and then you can change the “start date”. Alternatively, you can press the “x” button to clear the dates, and then set them as you wish.