553-5.7.1 Anyone understand this email delivery rejection?

I received this error message (in quotes) when I tried to email a lawyer:

“Google tried to deliver your message, but it was rejected by the recipient domain. We recommend contacting the other email provider for further information about the cause of this error. The error that the other server returned was: 553 553-5.7.1 sorry, that domain isn’t in my list of allowed rcpthosts
553-5.7.1 hm let me see …
553-5.7.1 hm does it look good ?
553-5.7.1 No! You are a bad guy!
553 5.7.1 sorry, that domain isn’t in my list of allowed rcpthosts (state 14).”

The strange comments at the end could be related to the content of my note. Any ideas what is going on? Did the lawyer do it on purpose?