don't try to use domain names you don't own. If you do, at some point in the future something bad will happen.
I own invalidemail.org.uk (fantastic for passive aggressively giving out email addresses to people you don't like but secretly want to see where they are going with their request). A national UK charity actually sends acknowledgement emails to firstname.lastname@example.org when a fundraiser registers for one of their challenges but doesn't provide an email (or opts for no email or something). Mostly I just get a name but for some I could reset the password for a fundraising totals page and one time they included some contact details. They have not responded to my emails so far