If you would like to delete a particular calendar in Leopard’s iCal, you get the dialog box that’s pictured above. If you choose the “Delete and Notify” option, Mail.app launches and starts sending messages to people who you have events scheduled with.
Why can’t I just delete a calendar without notifying the whole friggin’ world that I am deleting a calendar? Hello? Apple?
Well, with a simple hack you can: Using iCal Reply Checker from John Maisey. iCal Reply Checker is an iCal add-in that gives you options for how replies to meeting invites are dealt with. Just click Add to install, then select the Do not send reply emails option, as pictured below.
Go back to iCal and try to delete the calendar. It will pop up the same dialog box, but it will not send notifications when you click Delete and Notify.
If you wish iCal to return to default behavior, just click Remove on iCal Reply Checker.