Write from facts rather than momentum
Pause long enough to remove accusations, assumptions, and details that belong to someone else. For a message about how to reconnect with a former business partner, use this factual base: remind the person where you worked together, when, and what current topic makes the contact relevant.
Offer a proportionate next step
Match the size of the request to the relationship and to what the recipient can reasonably decide now. Make one modest request and give enough information for them to decline or redirect it. Make the immediate next step clear enough that the recipient can answer without reconstructing the entire history.
Protect privacy on both sides
Do not imply endorsement, exploit a former hierarchy, or send confidential material from the old relationship. Use official business, privacy, conflict, and procurement rules when commercial or regulated information is involved. Use the most private legitimate channel available and do not share the exchange to recruit support or pressure.