The zabbix_sender utility can use the "-c config_file" parameter, in this case it can extract the reference to Zabbix-server (hostname/IP-address and port number) as well as Agent's hostname (to avoid the "-s", "-p" and "-s" parameters usage). It is great; however, the keyword "Hostname=" in config file could be absent (or commented out) in many installations. The agent in this case use some algorithm for the hostname obtaining (check for the "HostnameItem" keyword in the config file, use the default "system.hostname" for it, etc.). However, zabbix_sender utility in this case requires the "-s" parameter obligatory, otherwise it fails.

It will great to have the zabbix_sender utility with the same logic for a hostname calculation if it called with "-c" parameter, but the "Hostname" absent in config file. In the simplest case, just to use the default "system.hostname" metric by some way (asking the agent, or just replaying the same logic as the agent). Of course, it should be consistent with the agent's results (for example, transforming the hostname to uppercase on Windows platform and keeping it "as is" otherwise).