The part where I read Mozilla's FAQ
I spent months building a mail server, and then found out I'd built Thundermail. Sort of. The self-hosted kind, with the enterprise bits bolted on, and no waitlist.
Here's how it went. I was reading the Thundermail pricing page the way you read a competitor's menu: casually, with a coffee, looking for nothing in particular. Then I hit the FAQ. Built on Stalwart. JMAP alongside IMAP and SMTP. Calendars and contacts. Bring your own domain.
I looked at my second monitor. On it was the inbuxa admin console, built on Stalwart, speaking JMAP alongside IMAP and SMTP, serving calendars and contacts to my own domains. I put the coffee down.
To be clear up front, since my lawyer-brain insists: inbuxa has nothing to do with Mozilla or Thunderbird. No code was borrowed, no plans were peeked at, and as far as I know nobody in Mozilla's org chart has heard of me. We just went shopping for a mail server at the same store and came home with the same one.
Carcinization, but for email
Biologists have a word for how unrelated crustaceans keep evolving into crabs: carcinization. Email has its own version. Start from a modern Rust mail server with first-class JMAP, add a decent web client, and everything evolves into Thundermail.
My path there was not a plan. It was a series of yak shaves:
- Stalwart is an excellent mail server, and the web clients pointed at it didn't do it justice. So I wrote ihasmail.
- ihasmail grew calendars, contacts, files and filters, because once you have JMAP you get greedy.
- Stalwart keeps a few features in its paid Enterprise Edition: tenants, masked email, undelete and friends. I wanted them under the AGPL, so I rebuilt them clean-room, from public docs and the standards.
- Then there was the list of things nobody had roadmapped yet, and the list of things that were on a roadmap with no date next to them. I have the patience of a man who has been running Linux since 1994, which is to say none. I built those too.
- At that point I had a fork, a console and a webmail. Calling it "a few patches" stopped being honest, so it got a name.
The name, for the record, is "inbox" as Tiny Tina would say it, the same way she says "Gearbox" in Borderlands. Mozilla went with "Thundermail." Reasonable people can disagree about which is better. They are wrong, but they can disagree.
Mozilla, meanwhile, needed a mail server for its own service and picked Stalwart too. Stalwart's team even reworked the spam filter for them this spring. So two projects started from the same foundation and walked toward the same shape from opposite ends: they're building a service, I'm building the thing you'd run the service on.
inbuxa's own mail moved onto the fork on 20 September 2026, in a 78-second window, rollback never touched. That was the moment it stopped being a hobby and became a product. It was about two weeks before the coffee incident.
The chart I made to calm down
When in doubt, make a table. Here's how the two stack up as of 5 October 2026, from each project's own site, roadmap and release notes. Thundermail is in beta and moving fast, so check their roadmap before quoting me.
| Feature | Thundermail | inbuxa |
|---|---|---|
| What it is | Hosted email service | Self-hosted suite: server, admin console, webmail |
| Status | Beta, invites in waves; full launch expected 2026 | v2026.10.5, released 5 October 2026 |
| Foundation | Stalwart | Fork of Stalwart 0.16.x; webmail built from ihasmail |
| Protocols | JMAP, IMAP, SMTP | JMAP, IMAP, POP3, SMTP, CalDAV, CardDAV, WebDAV |
| Webmail | Experimental: folders and message display | Mail, calendars, contacts, files, filters; works on phones |
| Admin console | Account dashboard: settings, domains, aliases | Every server setting, live delivery tracing, guided DNS publishing |
| Turn off legacy protocols | Not documented | IMAP, POP3, ManageSieve, per tenant or server-wide |
| Server-side filters | Not documented | Sieve, built in the webmail or via ManageSieve |
| Addresses | 1 inbox, 15 addresses, 3 custom domains; + aliasing | Masked addresses, one per site, revocable individually |
| Multi-tenancy | No | Yes, isolated tenants with their own admins and limits |
| Identity / SSO | TOTP MFA | SCIM 2.0 (Entra ID, Okta, Keycloak); per-domain LDAP, SQL or OIDC |
| Undelete | Not documented | Mail, files, events, contacts and filters, retention you set |
| Compliance | Privacy commitments | Audit log, legal holds, journaling, DLP, locked accounts |
| Encryption at rest | Not at launch; being explored | Up to your deployment |
| Mail auth | SPF, DKIM, DMARC; DNSSEC and DANE on the roadmap | Per-domain DKIM, inbound SPF/DKIM/DMARC, automatic Let's Encrypt |
| AI | Assist announced in 2025; not in current plan listing | Optional self-hosted LLM spam signal, off by default |
| Branding | No | Logos per server, tenant or domain |
| Observability | No | Delivery traces, metrics history, alerts |
| Scale-out | Mozilla's problem | Read replicas, multiple message stores |
| Migration | Import planned | Stalwart by documented procedure; tool for Exchange, Gmail and IMAP coming |
| VPN | No | Coming: ihasvpn's WireGuard server |
| Installer | Not needed | Coming: one installer for all three pieces |
| Data location | Germany | Wherever you put it |
| Storage | 30 GB mail, 60 GB Send | However many drives you own |
| Price | $6/month, paid annually | No license key, no seats, no paid tier |
| License | Open source, Stalwart-based | AGPL-3.0 (server and console -only, webmail -or-later) |
Sources: tb.pro, Thunderbird services roadmap, Thunderbird blog, Nov 2025, Thunderbird blog, June 2026, inbuxa.org, inbuxa-server releases.
So who wins?
Nobody, because they aren't playing the same game. Thundermail is a mailbox you rent from people you trust. inbuxa is the building you'd put mailboxes in. The overlap is the foundation, and the foundation is good, which is the whole reason we both picked it.
Thundermail is the right answer if you want great email and never want to think about port 25 again. Someone else holds the pager, the delivery reputation and the backups. It plugs straight into Thunderbird, comes with Send and Appointment, and $6 a month is less than the electricity my blade chassis eats in an afternoon.
inbuxa is for the people who were going to run a mail server anyway: the school IT shop, the small business with a closet rack, the open source org that wants its mail where its code is. Those folks need tenants, SCIM, legal holds, undelete and a console that tells them what broke. That's the half of the chart Thundermail leaves blank, and it should. A consumer mailbox has no reason to ship journaling.
In fairness to Mozilla, the honest column on my side has some "coming soon" in it. The installer and the migration tool aren't out yet, so today you build from source or pull the container and follow the docs. And the contributor count on inbuxa currently fits on one hand, using one finger. Help wanted.
No hard feelings
Honestly, this is the best possible outcome. When Mozilla bets its first email service on the same server you forked, that's not competition, that's validation with a nicer logo. Every bug they report upstream makes my base better. Every person they teach that JMAP exists is a person who might someday want to run it themselves.
So, Thundermail team, if you ever read this: congratulations on the launch, nice spam filter, and if any of your users ask "can I host this myself?", I know a cat with an envelope who'd love to meet them.
Everyone else:
- Poke at the demo, where every domain and person is made up but the software is real.
- Read the docs or grab the source from git.coffeylabs.org.
- Come argue with me at community.coffeylabs.org.
inbuxa is not affiliated with or endorsed by Mozilla, Thunderbird or Stalwart Labs. Stalwart is a trademark of Stalwart Labs LLC. Thundermail is Mozilla's, and the coffee was mine.