Prevent Outlook from automatically deleting meeting emails

In Outlook 2013 and 2016 (Office 365), this is under Options -> Mail -> under "Send messages":

Delete meeting requests and notifications from Inbox after responding.

It seems trivial but takes long time to find it.

Please see the screenshot:

In Outlook Web Access(OWA), Under

Options -> Calendar Options

Uncheck the following checkboxes:

• Automatically place new meeting requests on my calendar, marked Tentative
• Move out-of-date meeting requests and responses to the Deleted Items folder

In Outlook 2007 (not sure about other versions), go to

Tools -> Options -> E-mail Options -> Advanced E-mail Options

Uncheck

"Delete meeting request from Inbox when responding"

(3rd from the bottom)

An update for more current OWA (Outlook Web Access). Go to

Settings -> Calendar -> Events and invitations

and deselect

• "Delete Invitations and responses that have been updated" and
• "Delete notifications about forwarded events".