But is there any real benefit over Postfix + Dovecot other than "it's new and written in Rust?" Postfix and Dovecot have been around for decades and respect the Unix philosophy of doing one thing and doing it well.
For example, it automatically handles Let's Encrypt certs for you. You get JMAP, CalDAV, WebDAV, CardDAV, IMAP4rev2, DKIM/SPF/DMARC, MTA-STS, DANE, spam filtering, SQL+blob+object storage backends, search, clustering, OpenTelemetry, etc all in one tiny binary.
Downsides: some features are gated behind an enterprise version and I think the dev team is one guy, or at least it was a while ago.
Having ran both for a long time, I'm sticking with Stalwart from now on as long as development continues.
I treat this as an insurance policy. Even in this thread people mentioned how Maddy, which is an alternative modern full stack email solution in a single binary, lacks development efforts.
This is why we have this fantastic release for Stalwart - free shit.
Also as of now enterprise is for $0.2 per account per month which is extremely cheap unless somebody wants to build a big spam farm, of which as civilized Internet user I don't support. Obviously this might change, but even if you can always built multi-tenancy layer by yourself if you really need it - rest of the codebase is AGPL.
The only way to adopt Stalward is to drop everything else and use a single monolithic do-it-all?
Messages are stored in a bespoke format and not easily accessible directly?
It doesn’t sound like it’s made to be usable with other software. This isn’t an advantage in my book.
Between all the options, you can design incremental backups, snapshots, or whatever with 3rd party tools to write a script to backup your mailboxes to be restorable in any other email service or software. I have tested it with rsync, restic, database dumps, mc/aws-cli depending on the backends used, of which I have tried them all, and found it designed to be very straightforward.
The monolithic aspect is a necessary aspect of being built for HA and distributed environments that it is all the more impressive how versatile it is.
Suits my needs, but I can see why it wouldn't suit everyone's.