Cisco 300-720 SESA: Which feature must be used to address entry “550 Too many invalid recipients | Connection closed by foreign host.”

Question

A network administrator notices that there are a high number of queries to the LDAP server. The mail logs show an entry “550 Too many invalid recipients | Connection closed by foreign host.”

Which feature must be used to address this?

A. DHAP
B. SBRS
C. LDAP
D. SMTP

Answer

D. SMTP

Explanation

To address the issue of a high number of queries to the LDAP server and the error message “550 Too many invalid recipients | Connection closed by foreign host” in Cisco Email Security Appliance (ESA), the feature that should be used is SMTP (Simple Mail Transfer Protocol).

SMTP is the standard protocol used for sending and receiving email messages. In this scenario, the high number of queries to the LDAP server indicates that the ESA is attempting to validate the recipients of incoming email messages by querying the LDAP server. However, due to the excessive number of queries or incorrect configuration, the LDAP server may be overwhelmed or not responding properly, resulting in the “550 Too many invalid recipients” error message.

To address this issue, the ESA can be configured to handle recipient validation using the SMTP feature. By enabling recipient validation via SMTP, the ESA will validate the recipients of email messages directly through the SMTP protocol, rather than relying heavily on LDAP queries. This approach reduces the load on the LDAP server and can help mitigate the issue of high query volume and the associated error message.

To configure recipient validation via SMTP on Cisco ESA, you would typically perform the following steps:

1. Access the Cisco ESA’s administration interface, such as the web-based GUI.
2. Navigate to the appropriate configuration section for email policies or recipient validation settings.
3. Locate the settings related to recipient validation and select the option to use SMTP for recipient validation.
4. Configure any additional settings related to SMTP recipient validation, such as timeouts or maximum number of recipients per message.
5. Save the configuration changes and apply them to the ESA.

By enabling SMTP recipient validation, the ESA will perform recipient verification using the SMTP protocol, which is typically more efficient and reliable than relying solely on LDAP queries. This configuration change should help alleviate the high query volume and the “550 Too many invalid recipients” error message.

It’s worth noting that the other options mentioned in the question are not directly related to addressing this specific issue:

• DHAP (Domain-based Reputation scoring, Host-based Attacker Protection) is a feature in Cisco ESA that provides reputation-based scoring for domains and hosts to identify and block potential threats. While it helps in overall email security, it is not directly related to solving the LDAP query issue mentioned.
• SBRS (SenderBase Reputation Score) is a Cisco technology that provides reputation scores for email senders based on their historical behavior. It is used to identify and block email from potentially malicious senders. Again, it is not directly related to resolving the LDAP query issue.
• LDAP (Lightweight Directory Access Protocol) is a protocol used to access and manage directory information. In this scenario, LDAP is the service being queried excessively, causing the problem. Therefore, using LDAP itself would not address the issue, and instead, SMTP recipient validation should be used.

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