Hi
the below article should help you to crete a user defined dectionary
https://support.symantec.com/us/en/article.HOWTO126561.html
after creating the dictionary and add the email addresses in it
Create a content policy for inbound messages only and add a condition text in specific part of the message header "Envelope sender"
contains email address from dictionary and choose the created dictionary and then click save and choose what ever action you want
Thanks