Have been googling around for a solution to make check_mailq work (on Slackware64 14.1).
Finally found it at
https://www.cyberz.org/blog/2009/01/...o-read-output/. This is finally my configuration:
nrpe.cfg:
command[check_mailq]=sudo /usr/libexec/nagios/check_mailq -w 6 -c 50
and /etc/sudoers:
nagios ALL=(ALL) NOPASSWD:/usr/libexec/nagios/check_mailq
Hope it saves someone's time.
Jan