If you are having trouble with your user user’s mail filters not being applied correctly, you may see an error that looks a fair amount like this in /var/log/exim_mainlog at delivery time:
2014-12-10 15:45:34 1W1ixR-0005w9-JJ == firstname.lastname@example.org R=virtual_user_filter defer (-17): error in filter file: malformed numerical string "1.9"
If you do, it’s likely that your user has configured a score for mail filtering that contains a decimal in their email filtering. For a while cPanel would allow user filters configured through cPanel to use decimals, but Exim chokes on any number that isn’t an integer.
The fix is easy: Log in to the user’s cPanel, and correct the rule by making the string an integer.