Whenever sendmail starts running as a daemon, it places the same information that it logs into this ${daemon_info} macro. For example, the following syslog information:

starting daemon (8.10.1): SMTP+queueing@01:00:00

would cause the value of ${daemon_info} to become:

SMTP+queueing@01:00:00

As distributed, this ${daemon_info} macro is not used in the configuration file. It is, however, available to you for use in designing your own particular rule sets. Note that a $& prefix is necessary when you reference this macro in rules (that is, use $&{daemon_info}, not ${daemon_info}).

${daemon_info} is transient. If it is defined in the configuration file or in the command line, that definition can be ignored by sendmail.