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Comparison · Comms
Gromox vs Stalwart
A side-by-side editorial comparison of Gromox and Stalwart — release velocity, themes, recent moves, and the top alternatives to consider.
Shared themes:imap
Gromox vs Stalwart: at a glance
What is Gromox?
Gromox is filling in Exchange Web Services fast enough to matter for non-Outlook clients.
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.
What is Stalwart?
Stalwart is shipping email's next-generation auth stack while the specs are still in draft.
Stalwart is an all-in-one mail and collaboration server — SMTP, IMAP, JMAP, CalDAV, CardDAV and WebDAV in one binary — releasing every one to two weeks on the 0.16.x line. The last two months read as a standards campaign: DKIM2 and the full DMARCbis set in 0.16.12, VAPID push in 0.16.14, FreeBSD support in 0.16.13, and a run of IMAP extensions (UIDONLY, UIDBATCHES, MESSAGELIMIT/SAVELIMIT) in 0.16.17. Between the additions, most of each release is JMAP conformance repair driven by the jmap-test-suite.
Gromox vs Stalwart: editorial side-by-side
Gromox
2.5COMMS
Gromox is filling in Exchange Web Services fast enough to matter for non-Outlook clients.
◆ Current state
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.
◆ Where it's heading
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.
◆ Prediction
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.
Stalwart
5.0COMMS
Stalwart is shipping email's next-generation auth stack while the specs are still in draft.
◆ Current state
Stalwart is an all-in-one mail and collaboration server — SMTP, IMAP, JMAP, CalDAV, CardDAV and WebDAV in one binary — releasing every one to two weeks on the 0.16.x line. The last two months read as a standards campaign: DKIM2 and the full DMARCbis set in 0.16.12, VAPID push in 0.16.14, FreeBSD support in 0.16.13, and a run of IMAP extensions (UIDONLY, UIDBATCHES, MESSAGELIMIT/SAVELIMIT) in 0.16.17. Between the additions, most of each release is JMAP conformance repair driven by the jmap-test-suite.
◆ Where it's heading
The project is building toward being the reference implementation of the modern mail stack — JMAP first, with the classic protocols held at parity rather than left behind. The fix lists have shifted in character over these eight releases: less "feature does not work", more "spec detail is wrong", which is what a codebase looks like as it converges on conformance. Security and multi-tenancy fixes keep appearing alongside the protocol work, indicating real deployments are exercising the newer subsystems.
◆ Prediction
The next releases most likely track revisions to the drafts already implemented — DKIM2, JMAP push and the calendar drafts are all still moving — rather than adding another protocol surface. Expect continued JMAP conformance fixes until the test suite stops producing them.
Alternatives to Gromox and Stalwart
Other Comms products tracked by Sparkpulse, ranked by recent ship velocity. Each card links to a full editorial trajectory and lets you pivot into a head-to-head comparison with either Gromox or Stalwart.
Respond.io
respond.io is monetizing AI usage directly while putting an assistant that builds agents in every workspace.
VerneMQ
VerneMQ's 2.2.0 collects a year of cluster and connection fixes into one release.
Roundcube
Roundcube is shipping matched security pairs across 1.7 and 1.6 LTS, roughly monthly.
NanoMQ
An edge MQTT broker hardening for vehicles — and dropping the old embedded arches to do it.
Heymarket
Real features ship between the SEO posts: tags, webhooks, escalations, and now RCS via Twilio.
See all Gromox alternatives → · See all Stalwart alternatives →
Recent activity from Gromox and Stalwart
Latest ship moves from both products, interleaved chronologically. ⚡ = editorial spark.
- 13h agoStalwartIMAP gains UIDONLY, UIDBATCHES and message-limit extensions
- 8d agoStalwartJMAP delivery push arrives; strict relays stop rejecting calendar mail
- 15d agoStalwartFix-only release: JMAP semantics and a credential escalation
- 18d agoGromox3.9 makes room bookings and EWS meetings properly actionable
- 21d agoStalwartVAPID lands for JMAP Web Push
- 29d agoStalwartFreeBSD support, plus OAuth scopes for IMAP, SMTP and Sieve
- 1mo agoStalwartDKIM2 and the full DMARCbis suite ship in one release ⚡
- 1mo agoGromox3.8 splits the Information Store per store and extends IMAP
- 3mo agoGromox3.7 fixes shared calendars, EWS fields and Thunderbird discovery
- 4mo agoGromox3.6 lands the full EWS meeting, delegate and task surface ⚡
- 5mo agoGromox3.5 adds per-service listen directives and fixes notifications
- 6mo agoGromox3.4 adds pre-delivery junk shelving and tightens header handling
Frequently asked questions
What is the difference between Gromox and Stalwart?
Both compete on the same themes — imap — within Comms. Stalwart is currently shipping more aggressively (velocity 5.0 vs 2.5), with 0 editorial sparks in the last 30 days against 0. See the at-a-glance table above for a side-by-side breakdown of velocity, recent sparks, and editorial themes.
Is Gromox better than Stalwart?
Sparkpulse doesn't pick a winner — we score release velocity, not feature parity. Stalwart is currently shipping more aggressively (velocity 5.0 vs 2.5), with 0 editorial sparks in the last 30 days against 0. For your specific use case, the alternatives sections above list other Comms products to evaluate alongside.
What are the best alternatives to Gromox?
Top Gromox alternatives in Comms are ranked by recent ship velocity. Browse the "Gromox alternatives" section above for the current picks, or visit /alternatives/gromox for the full list with editorial commentary on each.
What are the best alternatives to Stalwart?
Top Stalwart alternatives in Comms are ranked by recent ship velocity. Browse the "Stalwart alternatives" section above for the current picks, or visit /alternatives/stalwart for the full list with editorial commentary on each.