The BBS software can check message titles and bodies for objectionable content. The BADWORDS.SYS file contains a list of words or phrases, one per line. A message will be held if it contains a word or phrase from the list.
Format of BADWORDS.SYS # List of words to check for in messages (or titles). If any are found, the message will be held badword1 badword2 bad phrase
There isn't a default file. If you want to use this facility you have to create your own. It goes in the BPQMailChat folder on Windows or the linbpq directory on Linux.