What happens if I attempt to send an invitation from the Calendar app to an email address that doesn't have an associated Apple ID? If I have a standard IMAP mail account set as my default on an iOS device and I then attempt to send somebody an invetation from the Calendar app, what happens if the recipient doesn't have an Apple ID - how will the invitation appear to them?

No documentation that I could find online makes reference to this situation; the only things I could find were concerning sending invitations to existing Apple IDs (at which point a notification is generated on the device itself), or about using Exchange Accounts - which again works differently. My assumption was that Apple must send an email of some kind to the invitee, but I want to get it tested.
I just tried with one of my friends' email. They receive the mail with buttons like accept, decline etc., and the info of the event of course. The said buttons have URL like: https://www.icloud.com/calendar/eventreply_full/en-gb/&lt;some Key&gt;&amp;cc=IN#reply=accept It was sent from noreply@email.apple.com but with my name in the Sender. 

.ics of the event, text and HTML files were also attached.