Exim’s logging isn’t too detailed by default, and in case of e-mail deliverability issues, provides insufficient information for proper diagnostics. So how do we extend Exim’s logging on cPanel systems?
This is a pure WHM action, so log into WHM as root, and navigate to Main >> Service Configuration >> Exim Configuration Editor
Scroll down to the bottom of the screen and enter the advanced editor mode by clicking on the Advanced Editor button.
When the Advanced Editor opens, put the following line into the first, topmost text box:
log_selector = +all -ident_timeout -host_lookup_failed -lost_incoming_connection
This will enable all extended logging attributes (+all), excluding the several ones that aren’t important but would fill logs with the excessive data (-ident_timeout -host_lookup_failed -lost_incoming_connection). While we are here, we will also close one security hole in Exim, that can enable a 3rd party to perform unauthorized relaying if left open.
If the following lines aren’t already in the first, topmost text box, add them as follows:
hostlist relay_hosts = 127.0.0.1
hostlist relay_from_hosts = 127.0.0.1
hostlist auth_relay_hosts = *
Scroll down to the bottom of the screen, and press the Save button. This will save your changes and restart Exim. Watch the output on the screen which, amongst other things, must read that Exim configuratin has passed test ie. that it is syntactically correct:
Configuration file passes test! New configuration file was installed.
and that Exim was successfully restarted:
Exim MTA…
Waiting for exim to restart…………..finished.
exim (/usr/sbin/exim -bd -q60m) running as mailnull with PID 26404
exim started ok
…Done
But Wait! We are not done yet! Now navigate to Main >> Server Configuration >> Tweak Settings and make sure that Track the origin of messages sent though the mail server by adding the X-Source headers (exim 4.34+ required) is turned ON. If it isn’t, turn it on by clicking on the little checkbox at the right end of the aforementioned line, scroll down to the bottom of the screen and press Save.
Done, we have expanded the Exim’s logging facilities (and message headers for all future messages) and implemented the anti-relay protection.
Now, tailing Exim’s main log in shell using the command
tail -f /var/log/exim_mainlog
We will notice that logs have started to provide much more extensive information.