A support desk/ticketing or sales pipeline service feels like the way to go here. Zendesk is a good low cost ticketing/support and Hubspot is marketing/sales. Y

A support desk/ticketing or sales pipeline service feels like the way to go here. Zendesk is a good low cost ticketing/support and Hubspot is marketing/sales. You could set it up so emails go through the service so you have the full history of the conversation in a single easy to read thread. You could then attach an SOW contract to the ticket and update the contract as the client’s needs evolve.