Which of the following best describes an MTA?
A. a list of recipients for which email will be accepted
B. a component that accepts email messages from a MUA
C. an email server
D. a list of rules that control which senders can connect to a listener
E. an email client
F. a component that delivers email messages to a user’s inbox
Explanation:
A Mail Transfer Agent (MTA) is best described as an email server. One example of an MTA is the Cisco Email Security Appliance (ESA). Cisco ESA is designed to protect against email threats, such as malware attachments, phishing scams, and spam. It is also designed to provide data loss prevention (DLP).
A Mail User Agent (MUA) is best described as an email client. When a MUA has an email message to send, it connects to a Mail Submission Agent (MSA). An MSA is best described as a component of an MTA that accepts email messages from a MUA, typically by using Simple Mail Transfer Protocol (SMTP). The MTA will look up the Mail Exchange (MX) Domain Name Server (DNS) record for the destination domain and will attempt to establish a connection to the destination MTA over SMTP. After the destination MTA receives the email message, another MTA component, the Mail Delivery Agent (MDA), will deliver the email message to a user’s inbox. The recipient’s MUA will typically retrieve the email message by using Internet Mail Access Protocol (IMAP) or Post Office Protocol (POP).
A Recipient Access Table (RAT) is best described as a list of recipients for which email will be accepted. Recipients can be accepted or rejected by domain name, partial domain, user name, or email address. The RAT is processed from top to bottom until a match is found. Typically, the RAT should contain only the local domain name.
Listeners on an email server listen for connection attempts. Public listeners are used for incoming email, typically from the Internet to the local network. Private listeners are used for outgoing email, typically from the local network to the Internet. RATs are used by public listeners, not by private listeners. Incoming email is accepted only if a corresponding entry is found in the RAT.
A Host Access Table (HAT) is best described as a list of rules that control which senders can connect to a listener. Hosts are defined within sender groups, and mail flow policies define how those sender groups can connect to the listener. The HAT is processed from top to bottom until a sender group match is found, at which point the corresponding mail flow policy will be applied.
The HAT is used by both public listeners and private listeners. For a public listener, the HAT is configured to accept email from all hosts by default. For a private listener, the HAT is configured to relay email only from internal mail hosts; all other hosts are rejected.
Reference: https://www.cisco.com/c/en/us/support/docs/security/email-security-appliance/215912-hat-rat-overview-common-errors-and-t.html CCNP and CCIE Security Core SCOR 350-701 Official Cert Guide, Chapter 10: Content Security, Cisco ESA