How does Plain group customers into tenants automatically?
Plain creates a tenant from a customer's email domain the first time they contact you, then adds later customers with the same domain to it. You can adjust this per tenant or turn it off for the workspace.
Note for workspaces created before September 2026: you still see Companies alongside Tenants. This is changing. Workspace admins will hear from us before anything moves, and Companies keep working as they do today until then.
When a customer writes in for the first time, Plain looks at the domain of their email address. If a tenant with that domain already exists, the customer is added to it. If not, Plain creates a new tenant, sets that domain as its primary domain, and adds the customer. For example, a customer writing from jane@nike.com is added to a tenant whose domain is nike.com.
Customers on free email providers such as Gmail are not grouped this way, since the domain does not identify a company.
The tenant page header shows where each tenant came from: created from a domain, created manually, or imported from your CRM. All three kinds work the same way once they exist.
Domains on a tenant
Each tenant has one primary domain and can have alternate domains. You can edit them on the tenant page under Domains. Plain uses the primary domain to fetch the tenant's logo.
Automatic joining
Each tenant has a setting that controls whether new customers with a matching email domain are added to it automatically. It is on for tenants Plain created from a domain, and off for tenants you created through the API or imported from a CRM. You can see and change it on the tenant page.
Tenant fields
You can create, edit and delete tenant fields in Settings, then Tenant fields, and choose which ones show on tenant pages and in the tenants list. Fields synced from a CRM keep their values in sync from the CRM.
Turning it off
Domain-based tenants can be turned off for the whole workspace in Settings. Turning them off does not delete anything. Existing threads keep their references, and you can turn the setting back on later.
Threads and tenants
A tenant created from a domain is never set as a thread's tenant, though it still counts when Plain works out the thread's tier. See Which tenant is assigned to a thread when a customer belongs to multiple tenants?.