PHP 5.4 is reached its end of life with no further security updates to be published after September. With this, we will be upgrading our PHP instances to version 5.6 on 11 September.
We had to perform an emergency reboot on the server after an unexpected firewall problem took the server offline. After about 10 minutes of downtime, all services are back to normal.
The server experienced a problem email deliveries earlier today.