When deleting items, Outlook normally does the following: For appointments, updates free/busy information and sends cancellations ...

When deleting items, Outlook normally does the following: 

 ·  For appointments, updates free/busy information and sends cancellations 
 ·  For delegated tasks, sends notification 
 ·  For contacts, removes significant dates from Calendar

Do you want these things done when these items are deleted? This will take more time.