I've attempted to change the hostname of my machine, now Nagios stopped sending out alert emails.
I've changed the hostname back using hostname oldhostname, however even after a complete reboot, nagios no longer works. Yes, it did work before and was sending out nofications just fine.
Also, doing a printf text | mail -s "test" emailaddress here works just fine as well.
Here's what my /etc/hosts file looks like:
Do not remove the following line, or various programs
that require network functionality will fail.
127.0.0.1 nag nag.101com.com localhost.localdomain localhost