When troubleshooting mail or attempting to discover the source of spam originating from your server, it is often useful to enable extended Exim logging. This can be done from from inside the WHM with no additional mailserver tweaking needed.
Log into your server's WHM interface and go to Main » Service Configuration » Exim Configuration Editor, scroll to the bottom and click the Advanced Editor button. In the first blank field enter the line given below. There are more options that can be used, including +all, however these are the ones we have found to be the most useful:
Click save and you're all set! You can now watch the exim log at
/var/log/exim_mainlog for additional info!