A retail mail server must always appear on one dedicated public address that maps to exactly one private address. Which translation is that?
Select an answer to reveal the explanation.
Short Explanation
This server needs its own street number, not a desk number inside a shared lobby. You map one dedicated public address to the mail server's one private address, which is one-to-one NAT. Sharing one public address among many hosts, picking a different public address per session, or forwarding one port on a shared address does not give the server that fixed identity.
Full Explanation
One-to-one NAT maintains a fixed mapping between one private address and one public address. Inbound mail can always find the retail server on that dedicated public address. Port address translation lets many hosts share one public address by source port. That fits a crowd of clients and not a server that must always appear as one dedicated address. A public pool is the tempting twin because the server does get a public address. The pool can change that address from session to session, so it is not the dedicated address the stem requires. Forwarding one mail port on a shared public address publishes the service and still leaves the server on an address other hosts use. Exam caveat: the translation still needs a policy that permits the mail ports. The mapping existing is not the same as the traffic being allowed. Operational check: from outside, confirm the dedicated public address reaches only this mail server, and confirm the translation table shows a fixed pair rather than a changing pool.