Start with the part that is verifiable
Separate the event you can describe from the motive or reaction you are guessing. For a message about how to set an after hours boundary with your manager, use this factual base: use recent examples, observable impact, and the work requirement rather than labels about personality.
Make one answerable request
Give the recipient one concrete question or next step instead of several emotional jobs at once. Ask for a specific change, decision, or working agreement and choose a time to review it. Make the immediate next step clear enough that the recipient can answer without reconstructing the entire history.
Leave the recipient in control
Do not diagnose, gossip, embarrass a colleague, or turn one incident into a judgment about their character. Move harassment, discrimination, threats, health risk, and retaliation into the appropriate protected process. A clear message remains useful even when the answer is no or no answer arrives.