How to stop apcupsd slaves from sending emails?

I have several machines running apcupsd which are network slaved to a master connected to the UPS. From time to time we get short (~5sec) power brown outs which the master sends out emails about. That's fine.

However, the problem is that the slaves also send out the same messages, which are redundant.

I see that in /etc/apccontrol actions are configurable like this:

    offbattery)
        echo "Power has returned on UPS ${2}..." | ${WALL}
    ;;

I can simply remove the pipe to wall, but is that the best way of doing it? The manual doesn't seem to cover suppression of messages.