apcupsd and wall+sendmail

I'm using apcupsd-3.8.6nb5 on NetBSD3.1/sparc64
After a power failure I have the following messages in /var/log/messages:

Jul 12 11:30:26 vega apcupsd[395]: Power failure.
Jul 12 11:30:26 vega /netbsd: set{u,g}id pid 18809 (wall) was invoked by uid 0 
ppid 14994 (sh) with fd 1,2 closed
Jul 12 11:30:27 vega apccontrol: Warning power loss detected.
Jul 12 11:30:29 vega apcupsd[395]: Running on UPS batteries.
Jul 12 11:30:29 vega /netbsd: set{u,g}id pid 7591 (sendmail) was invoked by 
uid 0 ppid 1 (init) with fd 1,2 closed
Jul 12 11:30:29 vega /netbsd: set{u,g}id pid 23870 (wall) was invoked by uid 0 
ppid 15383 (sh) with fd 1,2 closed
Jul 12 11:30:29 vega apccontrol: Power failure. Running on UPS batteries.
Jul 12 11:42:27 vega apcupsd[395]: Power is back. UPS running on mains.
Jul 12 11:42:27 vega /netbsd: set{u,g}id pid 29748 (sendmail) was invoked by 
uid 0 ppid 1 (init) with fd 1,2 closed
Jul 12 11:42:27 vega /netbsd: set{u,g}id pid 2714 (wall) was invoked by uid 0 
ppid 1889 (sh) with fd 1,2 closed
Jul 12 11:42:27 vega apccontrol: Power has returned...

What do wall and sendmail messages mean?
Did I misconfigure something?

Regards,
Thierry.