What is likely the cause of not receiving alert messages from a newly failed-over web server?

The situation describes a scenario where alert messages from a newly failed-over web server are not being received, pointing towards a possible network-related issue. The focus is on port configurations which are crucial for the communication of alert messages.

In this context, blocking outbound traffic on port 22 to the log server is likely to hinder the server's ability to send alert messages. Port 22 is typically used for SSH (Secure Shell) communications, which can also encompass secure log transmission. If the failed-over web server is unable to communicate with the log server over this port due to an outbound block, it cannot send its alert messages, resulting in a lack of notification.

While the other options may involve port configurations that are generally relevant, they do not directly affect the capability of the failed-over web server to send out alert messages specifically. For instance, ports 21 and 162 relate to FTP and SNMP (Simple Network Management Protocol) respectively, which, while they can be important for different types of server communications, are not directly responsible for the alerting mechanism in this scenario. Therefore, the blockage of outbound communication to the log server on port 22 is a critical factor leading to the absence of alert messages from the newly failed-over web server.