Inbox domains & mailboxes

This system supports both a shared root domain and per‑team custom domains.

Domain layout

• Root inbound domain is set via INBOX_ROOT_DOMAIN (API) and EMAIL_DOMAIN (worker).
• Custom domain is stored in teamInboxSettings.domain.
• Each organisation may also use a subdomain under the root (for example company1.in.plop.email).

Mailbox resolution rules

1. Custom domain configured

   • apps/api resolves the team by teamInboxSettings.domain = <domain>.
   • If a mailbox doesn't exist for the team, it is created on first inbound message.

2. No custom domain

   • If the inbound domain matches INBOX_ROOT_DOMAIN, the API looks up the mailbox by { domain: root, name: mailbox }.
   • If no mailbox exists for the root domain, the webhook returns 404.

3. Unknown non‑root domain

   • If the domain is not the root and there's no teamInboxSettings match, the webhook returns 404.

Tags and mailbox names

• support+billing@... stores the message under mailbox support with tag billing.
• mailboxWithTag is preserved as the full local‑part (support+billing).
• Tags are lower‑cased and searchable via the Messages API.