[BtM909]

I think this is also true for trivial / hypothetical examples. I used to work at a global company that would use 'acme' as an example domain, including for emails and such. Because when we started, the domain didn't exist so test emails would just disappear in void.

Until the domain was registered and is actively being used.

[SilasX]

There used to be a blog where someone registered DoNotReply.com and posted all the replies he got as a result of companies using that as a default reply-to in emails — which often included sensitive information.

It’s not around anymore but here’s a discussion of it when it was up:

https://boards.straightdope.com/t/donotreply-com/442816