Respond.io vs Gromox

Gromox ships a minor roughly every four to eight weeks and has moved from 3.0 to 3.9 in this window. The centre of gravity is EWS: 3.6 landed roughly two dozen operations at once — task CRUD, delegate management, calendar occurrences with timezones, full meeting invitation and cancellation lifecycle, read receipts — and every release since has extended or corrected it. Alongside that, 3.8 introduced a per-store split-process model for the Information Store and partial IMAP4rev2 support, and 3.9 made auto-accepted room bookings send confirmations and handle cancellations.

The project is working outward from MAPI compatibility toward the protocols that non-Outlook clients actually speak. EWS is the clearest case, but the same pattern shows in IMAP (custom keywords, IMAP4rev2 commands, SENT* keywords fixed to test the Date header as the spec requires) and in AutoDiscover fixes that unblocked Thunderbird. A second, quieter thread is offloading format conversion to external tools — Pandoc for HTML/RTF, Chawan for HTML-to-text — rather than maintaining converters in-tree. Meeting and calendar handling generates the most fix traffic, which is what you would expect from the hardest part of an Exchange-compatible server.

Expect EWS coverage to keep expanding toward whatever operations remain unimplemented, since that has been the consistent destination of feature work for five releases. The split-process Information Store introduced in 3.8 is the other thread to watch — a config bitmask suggests further isolation work is planned rather than finished.