Prevent pfishing calendar items

Is there no option in Outlook to prevent unwanted meeting invitations from being inserted into my Outlook calendar without my knowledge or consent? The only option I see is a choice among Automatically Accept, Automatically Decline Recurring Meetings, and Auto Decline Meetings that Conflict.

Lately I've been receiving two or three phishing attempts per week in the form of meeting invitations. Deleting them from the inbox does not prevent the calendar item from added to my calendar, whether or not the invitation message was opened. In other words, merely receiving the invitation adds it to my calendar. After the invitation message is permanently deleted, the calendar item remains. If I notice it, I can delete it. But phishing attacks are becoming steadily more sophisticated. I don't want those links in my Exchange mailbox. And I don't want to keep searching my calendar to delete them.