At 12:49 AM the client mail server which provides SMTP, IMAP, and POP3 for clients and web mail, crashed.
This is a virtual machine sitting on a physical host. The physical host was still running clean. This is the first time this particular machine has crashed since it was loaded in 2013, the software is stable. However, CentOS 6 did release a kernel upgrade in spite of the age of the software with absolutely no notes as to what they changed / fixed. I have applied this upgrade.
MySQL has also been somewhat unstable on the web server since an upgrade several days ago. I have downgraded MySQL to 5.7.15 which is the version prior to the recent upgrade which introduced instability.