J
Jonathan Dow
Email has a built-in interaction boundary in Missive: the subject line. Each new subject from the same address creates a new conversation. SMS has no equivalent — every message from a phone number lives in one conversation forever. For any business with repeat customers, that's one unbounded thread per contact, growing indefinitely.
Three paths — any one solves it:
  1. **Accept
    subject
    /
    thread_id
    /
    external_id
    on SMS drafts.** When different from the active thread, open a new conversation for that number. Mirrors email. (Currently silently dropped for SMS — support confirmed it's unsupported.)
  2. Add a "Close SMS conversation" action.
    Next inbound creates a fresh thread; old thread stays searchable on the contact.
  3. Expose conversation metadata at draft time
    that Missive honors as a secondary threading key.
Why it matters:
  • CRM and AI over SMS get dramatically cleaner — no prompt contamination, no custom filter layers per integration.
  • Team triage stops being "read six months of history to know what today is about."
  • Heavy SMS accounts are heading toward 10,000+ messages per contact with no archival path.
Not a new concept — just SMS catching up to email's threading model.