Pick the edition that fits your deployment.

Stalwart is built by a full-time professional team, not as a side project, and the Enterprise edition is what pays for that team and keeps the project sustainable. About 85% of Stalwart's features are free under AGPL-3.0; the Enterprise features are mostly ones that matter to large organisations and hosting providers running Stalwart at scale. Enterprise revenue pays for the work every Stalwart user benefits from: the engineers who ship a new release every week, security fixes within 24 hours of a report, an independent security audit every time a large part of Stalwart is rewritten, stress tests and benchmarks on dozens of cloud servers, and our work on email standards at the IETF. If Stalwart is valuable to your organisation, an Enterprise license is the most direct way to support it.

Yes. We understand the concerns raised by past incidents where popular open-source projects changed their licensing model or moved existing features behind a paywall. We have no intention of doing a "rug pull". Stalwart will remain under AGPL-3.0, and we will not reclassify any existing open-source feature into a paid one. The Enterprise edition exists solely to fund the long-term sustainability of the project. The open-source version continues to receive updates, enhancements and new features as part of our ongoing commitment to the community.

The Enterprise license includes additional features and integrations designed for large-scale or complex deployments: multi-tenancy with per-domain directory backends, multi-tenant branding, account archiving and un-deletion, the AI spam classifier with models from OpenAI, Anthropic, Google Gemini, Ollama or any OpenAI-compatible server, AI-assisted Sieve scripting, LDAP failover, read replicas, sharded blob and in-memory stores, live telemetry, message delivery history, dashboards and metric alerts. The full breakdown is in the table above and on the Enterprise edition page. To qualify for Premium Support, your organisation must subscribe to 150 or more mailboxes under the Enterprise license.

Enterprise licensing is sold per mailbox as a subscription, giving you a flexible and scalable model that fits any organisation. You only pay for what you need, billed annually or monthly, with a predictable cost structure. The pricing is tiered: the more mailboxes you license, the lower the per-mailbox cost. The full table is on the pricing page. After purchase you receive a license key that activates the Enterprise features. Keys are issued to a server domain name and can be used on an unlimited number of servers under that domain. For example, a license issued for *.example.org can be installed on mx1.example.org, mx2.example.org and any other server under example.org, with no additional licensing. Although the license is issued to a specific server domain, the deployment can still host an unlimited number of client domains: a license registered for *.example.org can serve mail for foobar.org, customer.com or any other domain your users send and receive mail under. The domain restriction applies only to the server hostnames, not to the domains the server provides email service for.

Upgrading is a fully automated process. Visit the Stalwart Labs Licensing Portal. Credit-card purchases are issued instantly, so your license key is available immediately and activates the Enterprise features as soon as it is installed on the server.

Yes. We offer a 30-day trial license with full access to every Enterprise feature, available at license.stalw.art/trial, so you can evaluate Enterprise in your own environment before committing.

If you cancel, the server reverts to the Community edition automatically. Enterprise-only features stop, but no data is lost and no service is interrupted: mailboxes, calendars, contacts, file storage and configuration remain intact, and standard email and collaboration service continues without disruption for your users.