Product Updates

Email Hosting on Your Domain, Built on JMAP and Stalwart

2026-09-14 · OSIR Team

Every domain registered at OSIR can now carry real mailboxes. Enabling email on a domain costs nothing, each mailbox is billed at one published package price, and the DNS work that usually eats an afternoon happens on its own if the domain sits on OSIR nameservers. Underneath it runs Stalwart, an open-source mail server written in Rust, and it speaks JMAP alongside IMAP, POP3 and SMTP. The email hosting page has the current packages and prices.

This post covers what you get, how the setup works, why JMAP matters, and what the eleven email tools on the OSIR MCP server let an AI assistant do with all of it.

What does OSIR email hosting include?

Packages are storage tiers. The current ones and their monthly and annual prices are on the email hosting page, which reads them from the same catalog the checkout uses, so the number you see there is the number you pay.

How do you set it up?

There are three steps, and for most domains the second one is automatic.

1. Enable email on the domain. Pick any domain in your account and turn email on. If the domain uses OSIR nameservers, every required DNS record is published in the same request and the domain is active immediately.
2. Or verify external DNS. If your DNS lives elsewhere, the response lists the records to add. Paste them in at your DNS host, click verify, and the domain flips to active once they resolve.
3. Create mailboxes. Choose an address and a package, monthly or annual. The generated password is shown exactly once, so store it before you close the dialog. You can change it any time afterwards.

One detail that matters if you already have email somewhere else: OSIR will not silently take over a domain that is receiving mail at another provider. If it finds an existing MX record pointing elsewhere, or an SPF record that authorizes other senders, it stops and asks you to confirm the change explicitly. Nothing moves until you say so.

Why JMAP, and what is wrong with IMAP?

IMAP was designed in 1986 for a terminal with a permanent connection to a mail server. It has been patched for forty years, and every mail client works with it, but the design shows. A client opens one folder at a time, keeps a connection open per folder to hear about new mail, and re-scans message flags on each visit. On a phone with a weak signal, that is slow and expensive on battery.

JMAP (JSON Meta Application Protocol) is the IETF standard written to replace it, published in 2019 as RFC 8620 for the core protocol and RFC 8621 for mail. It sends JSON over HTTPS, so it passes through any firewall and proxy that allows web traffic. One request can fetch folders, messages and threads together. Sync is incremental, so a client asks for what changed since a state token rather than re-reading the folder. New mail arrives by push, with no connection held open.

Stalwart implements JMAP natively rather than as a translation layer over an IMAP store, which is one of the reasons we chose it. Fastmail, whose engineers wrote the JMAP specification, runs its own service on the protocol. Our webmail talks JMAP to the server. Desktop and mobile clients that still speak IMAP connect exactly as before, and nothing about your existing setup has to change.

What can an AI assistant do with it?

The whole flow is exposed on the OSIR MCP server as an email hosting group of 11 tools: listMailPlans, getMailboxQuote, enableMailDomain, listMailDomains, getMailDnsRecords, verifyMailDns, createMailbox, listMailboxes, setMailboxPassword, deleteMailbox and getMailboxUsage.

In practice that means you can tell Claude or any MCP client "set up hello@ and billing@ on example.com on the smaller package, billed yearly" and it will enable the domain, quote both mailboxes with the exact charge, and wait for your confirmation before creating them. The password for each new mailbox comes back once in the reply, the same way it does in the dashboard. Mailbox usage and DNS verification are read-only tools, so an assistant can check on things without being able to spend anything.

If you are connecting an assistant for the first time, the MCP page has the connector URL and a two-minute setup.

Email hosting FAQ

What does enabling email on a domain set up, and why is it free?

The hard part of email hosting is the DNS setup, and we wanted to remove it. Enabling a domain points every required record at your domain in one step, with the configuration that keeps your mail out of spam folders: MX for delivery, SPF to name the servers allowed to send for you, a DKIM key so every outbound message is signed, a DMARC policy so receivers know what to do with mail that fails those checks, and MTA-STS so delivery to you is encrypted. Getting any of these wrong is the usual reason a new domain's email lands in spam. You pay only for the mailboxes you create afterwards.

Can I keep using Outlook, Apple Mail or Thunderbird?

Yes. Every mailbox accepts IMAP and SMTP connections as well as JMAP, so any existing client works unchanged. Clients that support JMAP, and the included webmail, use the faster protocol.

Do I need to configure MX, SPF, DKIM or DMARC myself?

Not if the domain uses OSIR nameservers. Those records, plus MTA-STS and autoconfig, are published automatically when you enable email. For domains with DNS elsewhere, OSIR returns the exact records to add and verifies them when you ask.

What happens to my existing email if I enable OSIR email on a domain?

OSIR checks first. If the domain already has an MX record pointing to another provider, or an SPF record that authorizes other senders, it refuses to proceed until you explicitly confirm the takeover. Mail already delivered elsewhere stays where it is; new mail arrives at OSIR once you switch.

How is a mailbox billed?

Per mailbox, on the package you choose, monthly or annually, auto-renewed from your OSIR balance. A deleted mailbox keeps its data for 14 days before removal.

Can an AI agent create mailboxes for me?

Yes, through the 11 email tools on the OSIR MCP server. Anything that costs money is quoted first and only executed after you confirm, and the generated password is shown once in the assistant's reply.

Image generated with AI (Higgsfield).