Thanks, Andrea.
But I guess even those totally clear instructions don't seem to be giving me the expected result. I've added links to three screen captures.
1. Logged in as System Admin, selecting the domain and "Edit" to show the settings.
https://onedrive.live.com/redir?resid=B1EB52E4700298E0!262377&authkey=!AIWnP3Sd9vUgwQ0&v=3&ithint=photo%2cpng
2. Logged in as Domain Admin, selecting System, Domain. And as you will see, the option is not there.
https://onedrive.live.com/redir?resid=B1EB52E4700298E0!262378&authkey=!ADtDON0EPvyQ7Mk&v=3&ithint=photo%2cpng
3. Logged on as Domain Admin selecting Auto-Responder and the option to change it not available.
https://onedrive.live.com/redir?resid=B1EB52E4700298E0!262376&authkey=!AHIyIp12WJc53v8&v=3&ithint=photo%2cpng
So, I must still be doing something wrong. :( Also, I'm assuming that "impersonate" is the same permissions wise as logging in with a username and password for the domain admin account.
Well, I tried to use hyperlinks but got an error that my account does not have permission to use them so I'm going to try just posting the links and see what happens.