Received from J_Catlady at 9/7/2018 08:04 PM UTC:
I would change them all of these entires to start with "Message rejected," making the word "rejected" unambiguously an adjective rather than an action.
In the original "Rejected message" the word "rejected" could be an adjective or a verb, but in the proposed "Message rejected" it's a verb (past tense). English language syntax doesn't place adjectives AFTER the noun they modify or describe. The proposed change only adds confusion.
Perhaps "System rejected message..."