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 end a business partnership professionally, use this factual base: state the role, agreement, effective date, unfinished work, property, access, and any transition obligation.
Make one answerable request
Give the recipient one concrete question or next step instead of several emotional jobs at once. Give a clear ending, complete the required handoff, and name what support you can realistically provide. Make the immediate next step clear enough that the recipient can answer without reconstructing the entire history.
Leave the recipient in control
Do not disappear, promise indefinite availability, or use the ending to relitigate every grievance. Follow contracts, safeguarding, data access, employment, custody, and legal requirements before the role ends. A clear message remains useful even when the answer is no or no answer arrives.