On CentOS, you can encounter the following behaviour when configuring an nrpe plugin with sudo:

/usr/lib/nagios/plugins/check_nrpe -H 1.2.3.4 -c check_exim
Mailqueue WARNING - query returned no output!


Given that check_exim is defined as follows, in nrpe.conf:

command[check_exim]=/usr/lib64/nagios/plugins/check_eximmailqueue -w 50 -c 100

And given (for completeness) its relative /etc/sudoers line as follows:

nagios ALL=(ALL) NOPASSWD:/usr/lib64/nagios/plugins/check_eximmailqueue

Then the problem is in the requiretty options in /etc/sudoers, enabled by default on CentOS. Simply comment it as follows:

#Defaults requiretty

After that the plugin should work as expected:

/usr/lib/nagios/plugins/check_nrpe -H 1.2.3.4 -c check_exim
Mailqueue OK - 11 messages on queue