Our Nagios server has stopped sending email notifications. If I run the notify-by-host or notify-by-service commands directly, I get email, and everything works as I expect.
When a notification is triggered, or if I trigger a custom notification, I can see the host notifications coming up in nagios.log, but nothing is showing up in mail.log and I receive no emails.
Everything was working fine a couple weeks ago.
Try running the commands from nagios user for debug