[CentOS] System Start-Up Issue Progress

On 07/04/2017 09:21 AM, Chris Olson wrote:
> It remains a mystery what could have happened during a standard yum
> update of the system to cause this domain and/or host related sendmail
> issue.


Run "hostname".  Has the hostname changed?  Run "ls -l /etc/hosts 
/etc/resolv.conf".  Have those files changed recently?

It's possible that this system was working in the past because its 
hostname was set up in DNS, and was removed.  In that case, the problem 
wasn't related to "yum."   sendmail would (IIRC) continue working after 
the system's hostname was removed from DNS, until the next time the 
system rebooted.