If we need to forward all outgoing emails from a particular domain to an email address, follow the steps given below.
Step1: Open the file '/etc/cpanel_exim_system_filter'
Step2: Append the below lines to the file
if $h_from: contains "domain1.com"
unseen deliver "firstname.lastname@example.org"
Here we need to replace domain1.com with the actual domain and email@example.com with the email address to which you want to forward the mails.
Step3: Save the file and close it
Step4: Restart exim service