Centrinity First Class Internet Services 5.50 allows for the circumventing of the default 'spam' filters via the presence of '<@>' in the 'From:' field, which allows remote attackers to send spoofed email with the identity of local users.
https://exchange.xforce.ibmcloud.com/vulnerabilities/6192
http://archives.neohapsis.com/archives/bugtraq/2001-02/0440.html