When a single client contact has multiple entities under one email address, how do you keep client communications organized in the system?

Communications are set up around a main company record for monthly/coaching clients. Everything goes into that business company record unless it's specific to the client's personal return, in which case it's tracked separately under a linked "personal" company record. This mirrors how many business owners want their personal tax matters kept distinct from their business matters, even though the same contact interacts on both.