For some reason our Nagios 3.2.2 box running on Ubuntu Server 10.04 has decided to stop sending out email alerts. Previously it was sending alerts perfectly fine.
Nagios Evenlogs show
[11-02-2011 12:13:25] Warning: Attempting to execute the command "/usr/bin/printf "%b" "***** Nagios ***\n\nNotification Type: PROBLEM\nHost: DURAP01\nState: DOWN\nAddress: 192.168.4.4\nInfo: (Host Check Timed Out)\n\nDate/Time: Fri Feb 11 12:13:25 GMT 2011\n" | /bin/mail -s " PROBLEM Host Alert: DURAP01 is DOWN **" firstname.lastname@example.org" resulted in a return code of 127. Make sure the script or binary you are trying to execute actually exists...
Postfix is working correctly as I’m able to send emails perfectly fine using sendmail.