Hi, I am in the process of setting up an mail content filter template to block postings with certain keywords in the subject line.

I am unable to match messages with "xyz:" in the subject line, and the docs don't have sufficient examples in regards to expression matching. 

I understand that "subject::" matches any empty string, but I am not sure how to setup [subject: "xyz:" ] to match any subject line that starts with "xyz:"

How can I setup content_filter to match any subject line that starts with "xyz:" ? and how do I escape the ":" in the string?

Thank you!