The letters that form the value of the DaemonPortOptions=Modify option (See this section) are stored in the ${daemon_flags} macro when the daemon first starts up. If the Modify was not specified for that port, the value stored in ${daemon_flags} is an empty string.

When a value is stored in ${daemon_flags}, each letter in that value is separated from the others by a space, and capital letters are doubled. If that option, for example, is declared like this:

DaemonPortOptions=Modify=bcE

the value of the ${daemon_flags} macro will become:

b c EE

Capital letters are doubled so that they can be detected in rules. Recall that rules view their workspace in a case-insensitive manner (that is, e is the same as E). Doubling allows the LHS of rules to be designed like this:

R $* e $*   match a lowercase E
R $* ee $*  match an uppercase E

${daemon_flags} is not used in the default configuration file, but is available for you to use in rules of your own design. Note that a $& prefix is necessary when you reference this macro in rules (that is, use $&{daemon_flags}, not ${daemon_flags}).

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