These are a couple things I tweaked in exim to help with the spam - mind this is a low volume server - so your mileage may vary.. I am new to Exim, there are surely better ways to do this, but immediately helped out without getting deep into exim.

1. Adding some delays to the SMTP transaction - this drops the impatient spammers...

At the end of the acl_mail block add a delay for everyone

    accept
        delay = 5s

Add this to the end of the acl_connect block

# Lets delay everyone for now to 8s for connecting...
    accept
        delay = 8s

2. Change the subject for spam emails - without digging into Spam Assassin configs and the cpanel way things are done, emails that were scored as spam - wanted "spam" prepended to the subject. Added this snippet below to help the case - set this in my own /etc/custom_exim_system_filter file. This is global on the server for incoming email. Additionally, I have seen emails over 4 "pluses" are definitely spam the past 2 weeks since implemented this.

if $message_headers matches "X-Spam-Bar: \\\\+\\\\+\\\\+\\\\+" then 
  headers add "Old-Subject: $h_subject:"
  headers remove "Subject"
  headers add "Subject: *Spam*  $h_old-subject"
  headers remove "Old-Subject"
endif

Cpanel was overwriting my changes to the default file, so copied, added this chunk then configured cpanel to use my version of the file - again, to prevent overwriting when cpanel updates.