Tenants

Multi-tenancy allows several independent organisations, referred to as tenants, to share the same Stalwart deployment while keeping their data and resources isolated from one another. A tenant is a logical division within the server: it has its own accounts, groups, mailing lists, and domains, and principals that belong to one tenant cannot reach resources that belong to another.

Each tenant is represented by a Tenant object (found in the WebUI under Management › Directory › Tenants). Principals associated with a tenant (accounts, groups, lists, and similar) carry a memberTenantId field referencing the owning tenant and are restricted to resources of that same tenant.

Permissions granted within a tenant are bounded by the tenant's own permissions. If a tenant administrator assigns a permission to a principal that is not enabled on the tenant, the grant has no effect. This ensures a tenant cannot exceed the privileges allocated to it at the server level.

Enterprise feature

This feature is available exclusively in the Enterprise Edition of Stalwart and is not included in the Community Edition.

Properties

A Tenant object exposes the following fields:

• name: the tenant's name, used as its identifier in the system.
• logo: a URL or base64-encoded image used when rendering the tenant in the WebUI.
• roles: the roles assigned to the tenant itself, modelled as a Roles variant that can be either the default role set or a custom set referencing specific roles.
• permissions: the permissions the tenant is allowed to grant to its principals, modelled as a Permissions variant (Inherit, Merge, or Replace) combined with an explicit enable/disable list.
• quotas: a map from TenantStorageQuota keys to numeric limits. This includes the tenant's total disk quota and the maximum number of principals of each kind (accounts, groups, lists, domains) that the tenant can create.
• usedDiskQuota: the amount of disk space currently consumed by the tenant, computed by the server.

The name field carries the tenant's human-readable label. There is no separate description field on the Tenant object.

Isolation, quotas, and custom role sets together allow multi-tenant operation, while still giving administrators the ability to regulate how much of the server each tenant can consume.

Quotas

A tenant's disk quota is the maximum storage consumed by all of its members combined. The sum of every member's used storage must fit within this value. For example, when a tenant has a 100GB quota, if member A has consumed 60GB and member B has consumed 40GB, no further mail can be accepted for any account in the tenant until usage is reduced.

Tenants also carry principal-count quotas, which limit the number of accounts, groups, lists, or domains the tenant can create. Both kinds of quota are expressed through the tenant's quotas map.

Branding

Stalwart supports per-tenant branding in the WebUI through the logo field on the Tenant object. The logo is displayed when a user belonging to the tenant accesses the WebUI, letting each tenant present its own visual identity in multi-tenant deployments.