Currently I am porting an old Nagios setup on a discontinued domain to a new domain. My Nagios is configured as well as sendmail to e-mail the IT department about down services. However in order for the e-mails to be received, Nagios needs to send the notifications from a valid user and NOT nagios at localhost.localdomain otherwise the e-mails get dropped. I do not have control over the SMTP relay or e-mail servers so I can not just allow these e-mails to come through.
I have looked all over for a way to configure this but I can’t seem to get it working. My notifications work if I point them to a different SMTP relay, so I know that my sendmail configuration is correct. I understand that this may also be a sendmail issue and not something that can be controlled by Nagios, but I figured if Nagios is sending the notifications maybe there is a way to send those notifications as someone specifically. I will post any configs that you think will help solve the issue. I am running Centos 5 with Nagios 2.12.