The Problem
On Gmail accounts, messages that belong to a single conversation are split across several separate threads when their subject lines differ, even though the messages are correctly linked to one another by In-Reply-To / References headers. One discussion ends up fragmented into multiple threads.
Proposed Solution
An option to thread by the In-Reply-To / References headers instead of Gmail’s X-GM-THRID thread id would keep these conversations grouped correctly.
Alternative Solutions
Context
This shows up in email-based development on mailing lists (Linux kernel mailing list style). A patch series is posted as one thread: a cover message, then each patch as a reply. The messages are linked by headers, but by convention each carries a different subject, e.g.:
- [PATCHSET] cover letter
- [PATCH 1/3] subsystem: do X
- [PATCH 2/3] subsystem: do Y
- [PATCH 3/3] subsystem: do Z
Mailspring shows these as separate threads, so the series and its review discussion become hard to follow. This is already a sore spot in Gmail’s own web UI and it carries over to Mailspring on Gmail accounts.