Hey, this would be pretty hard to achieve, unless you would be satisfied with a separate setting where you can enter custom filter for exact "characters", meaning if a message contains only one word, which is in your list, then it's marked as spam. So you would have a new list, eg. "m, f" and if a stranger writes an exact message saying "m" only (no words after/before), then it's a spam. It's also possible to match it per word (not per whole message), just let me know what's better for you.