(could mean shell command ended by signal 127 (Unknown signal 127)) from command: /usr/bin/php exim filter

This error means that the exim is trying to deliver the queue as nobody (exim security) and it does not have access to certain files used by the script for writing. This could be in most cases the log files inside the script directory.

An easy fix to this problem is to provide full permission (chmod 777) to the log files or files that script writes information to, so that the exim queue runner can access and write to log files or other files mentioned by the script.

chmod 777 /path/to/logs/of/script