The sendmail program can listen for (await) inbound connections on more than one interface, where each interface can have one or more addresses associated with it. The ${daemon_addr} macro contains the address upon which the daemon was listening when it accepted the inbound connection. This macro is given the value declared by the DaemonPortOptions=Addr option (See this section) associated with that connection each time rule sets are called.

The format of the value stored in ${daemon_addr} is based upon the setting of the DaemonPortOptions=Family option (See this section). If that setting is inet (the default) or inet6, the address in ${daemon_addr} will correspondingly look like one of the following:

123.45.67.89              an IPv4 address
IPv6:2002:c0a8:51d2::23f4 an IPv6 address

If the DaemonPortOptions=Addr option is undeclared, the default (with the inet family's format) becomes 0.0.0.0 for IPv4, or (with the inet6 family's format) IPv6::: for IPv6.

This ${daemon_addr} macro is not used in the rule sets supplied with sendmail. It is, however, available for your use when designing custom rule sets. Note that a $& prefix is necessary when you reference this macro in rules (that is, use $&{daemon_addr}, not ${daemon_addr}).

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