The Blocked Senders List relies on the "From" header. In the absence of robust email authentication protocols (SPF, DKIM, DMARC), attackers can easily spoof the "From" address.
A modern phenomenon discussed in security papers is the abuse of the block list mechanism, known as or List Bombing . outlook blocked senders list
Here is an analysis of the topic formatted as a technical brief/white paper. The Blocked Senders List relies on the "From" header
