We have been plagued with a recent rash of hardware and software problems as of late.
A current problem I am seeing is the older Redhat 6 servers are mysteriously powering themselves down.
It may be related to kernel upgrades I attempted recently. The newer kernels required a newer version of acpid. The acpid daemon is a program that listens to things like power and reset buttons and then acts accordingly.
I had to back out the kernels because the mandatory locks which mail really requires to operate properly were broken under 4.8 at least. I neglected to back out the updates to acpid at the same time.
In addition, on mail, sogo, a package we have in place to provide some interoperability with ms-exchange clients, overwrote some of the system python modules and broke some of the admin tools.
I’ve fixed these things and I’ve turned on some additional logging so that if it happens again it will hopefully provide additional information for troubleshooting.