Which option describes the difference between public and private listeners?

Question

Options

• AOnly the public listener can be configured to process incoming mail.
• BBoth can be used for inbound and outbound traffic.
• CPublic listeners can be configured to use port 80.
• DPrivate listeners do not have a host access table.

• A
  93% (42)
• B
  4% (2)
• C
  2% (1)

Explanation

Option A is correct because, in the context of Cisco Email Security Appliance (ESA), public listeners are specifically designed to accept inbound SMTP connections from external senders (the internet), while private listeners are reserved for relaying outbound mail from internal mail servers - so only public listeners handle incoming mail.

B is wrong because the two listener types have distinct, non-interchangeable roles: public handles inbound, private handles outbound - not both directions for either type.

C is wrong because email listeners operate on SMTP port 25 (or 587 for submission), not port 80, which is HTTP; this distinction applies equally to both listener types.

D is wrong because both public and private listeners have a Host Access Table (HAT) - the difference is in how the HAT is configured, not whether it exists; private listener HATs typically allow trusted internal relay hosts.

Memory tip: Think of the labels literally - a public listener faces the public internet and accepts mail into your organization, while a private listener stays on the private internal network and sends mail out. Public = incoming, Private = outgoing.

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