Beginning with V8.7, the ${opMode} holds as its value the operating mode that sendmail was started with. The operating mode is set with the -b command-line switch (-b). For example, if sendmail were started as a daemon with -bd, the value in ${opMode} would become d.^[20]

^[20] Because the LHS of rules are case-insensitive, you cannot use just this macro to detect the difference between -bd and -bD.

Once set, ${opMode} retains its initial value as long as sendmail runs. It can be changed only by defining it in the configuration file (not recommended). Currently, ${opMode} is used only in rule sets by the redirect feature (FEATURE(redirect)). Because ${opMode} generally does not change once it is defined, you need not prefix it with $& when using it in rules.