How can the configuration be tested, using telnet, from outside the local network?

On a newly-installed mail server with the IP address 10.10.10.1, ONLY local networks should be able to send email.

How can the configuration be tested, using telnet, from outside the local network?

A.
telnet 10.10.10.1 25
MAIL FROM<[email protected]>
RECEIPT TO:<[email protected]>

B.
telnet 10.10.10.1 25
RCPT FROM:[email protected]
MAIL TO:<[email protected]>

C.
telnet 10.10.10.1 25
HELLO bogus.example.com
MAIL FROM:<[email protected]>
RCPT TO:<[email protected]>

D.
telnet 10.10.10.1 25
HELO bogus.example.com
MAIL FROM:<[email protected]>
RCPT TO:<[email protected]>

E.
telnet 10.10.10.1 25
HELO: bogus.example.com
RCPT FROM:<[email protected]>
MAIL TO:<[email protected]>