For reasons unknown to me, the server does not like certain words. For example, if you were to include certain common names of various drugs in your message, ie one beginning with H or V, the server will bounce you with that message.
If you use certain terminology related to breaking into computers, the result is the same.
Context doesn't matter ie. "I think I'd need to be on H..... to moderate this forum. V..... does not dull the pain sufficiently", is something that the server has no sense of humour about
My advice is to replace a few words and see what happens then.