Threadkept, one thread per decision

Field notes

Threadkept structures a project as a list of questions rather than as a chat stream or task board. Participants can attach drawings, estimates, and photos to each question, then reply through ordinary Gmail or Outlook messages. A decided thread keeps its answer at the top while preserving the underlying conversation. The site also describes sender verification through SPF, DKIM, and DMARC and says files remain associated with their threads.