Explanation
To allow X connections to be forwarded from or through an SSH server, the configuration keyword that must be set to yes in the sshd configuration file is XllForwarding. This keyword enables X11 forwarding, which is a mechanism that allows graphical applications to be run on a remote host and displayed on a local host. The sshd configuration file is usually located at /etc/ssh/sshd_config, and the XllForwarding keyword can be set globally or per host. For example:
XllForwarding yes
This will enable X11 forwarding for all hosts. To enable X11 forwarding for a specific host, use the Match directive, followed by the Host keyword and the host name or pattern. For example:
Match Host example.com XllForwarding yes
This will enable X11 forwarding only for the host example.com.
References:
X11 Forwarding using SSH
sshd_config - OpenSSH SSH daemon configuration file
How To Configure X11 Forwarding Using SSH In Linux

Explanation
DNSSEC adds digital signatures to DNS records, which can be verified by the clients using public keys. This way, DNSSEC ensures that the DNS responses are authentic and have not been tampered with by attackers. DNSSEC does not encrypt DNS queries or answers, nor does it authenticate the user or the nameserver123 What is DNSSEC on DNS Server in Windows Server?1


How DNSSEC Works | Cloudflare

Explanation
The command that displays an overview of the Postfix queue content to help identify remote sites that are causing excessive mail traffic is qshape. This command shows the number of messages in the active, deferred, and hold queues, grouped by the next-hop domain name. It also shows the age distribution of the messages in each queue, which can help to identify domains that are slow or unreachable. The output of qshape looks like this:

The first column shows the next-hop domain name, or TOTAL for the sum of all domains. The second column shows the total number of messages in the queue for that domain. The remaining columns show the number of messages in different age ranges, in minutes. For example, the T column shows the number of messages that are less than 5 minutes old, the 5 column shows the number of messages that are between 5 and 10 minutes old, and so on. The last column shows the number of messages that are older than 1280 minutes (about 21 hours).
The qshape command can be used with different options to specify the queue name, the domain name pattern, the bucket size, the bucket count, the sort order, and the output format. For more information, see the qshape man page1.
References: You can find more information about the qshape command and its usage in the following resources:
qshape - Postfix queue analysis tool
Postfix Queue Management

Explanation/Reference: https://www.ssh.com/ssh/keygen/