Creates a mailbox. The address is `local_part@domain`. The domain defaults to `inbox.ai`, Bird's shared mailbox domain, where creating the mailbox claims the address for your organization — first come, first served, and reserved to your organization even after the mailbox is deleted. You may instead name one of your own domains that is enabled for receiving email. An omitted local part is generated. On a custom domain, addresses of deleted mailboxes are quarantined: the same workspace can rebind one 30 days after deletion, other workspaces never can. The local part of the mailbox address (the part before `@`). Letters, digits, dots, underscores, and hyphens; stored lowercase. On the shared `inbox.ai` domain, separators must sit between letters or digits (no leading, trailing, or repeated separators), reserved names such as `postmaster` or `abuse` are unavailable, and choosing your own local part uses one of your plan's custom-handle allowance slots (generated addresses are always available). Omit to have Bird generate a random local part. The domain the address lives under. Defaults to `inbox.ai`, Bird's shared mailbox domain, where creating the mailbox claims the address for your organization: first come, first served, and permanently reserved to your organization even after the mailbox is deleted. May instead name one of your own domains that is enabled for receiving email. Display name used as the sender name on mail from this mailbox. Default Reply-To address stamped on mail sent from this mailbox. Which inbound mail the mailbox accepts. `open` accepts everything not blocked by a rule; `replies_only` accepts only replies to messages this mailbox has sent (a reply must match a message the mailbox sent, not merely land in an existing thread); `allowlist` accepts only senders matching an allow rule; `drop` stores nothing. Possible values: `open`, `replies_only`, `allowlist`, `drop` How long the mailbox remembers message metadata and extracted text. Original rendered source is always available for 30 days regardless of tier. Only `30d` is available today; longer tiers (`90d`, `1y`, and beyond) are coming soon. Possible values: `30d` Your own key/value data to attach to the mailbox. Up to 2 KB; keys starting with `__bird` are reserved. Mailbox ID. The mailbox's email address. Immutable once created. Display name used as the sender name on mail from this mailbox. Null when unset. Default Reply-To address stamped on mail sent from this mailbox. Null when unset. Which inbound mail the mailbox accepts. `open` accepts everything not blocked by a rule; `replies_only` accepts only replies to messages this mailbox has sent (a reply must match a message the mailbox sent, not merely land in an existing thread); `allowlist` accepts only senders matching an allow rule (replies to prior outbound are always admitted unless blocked); `drop` stores nothing. Possible values: `open`, `replies_only`, `allowlist`, `drop` Lifecycle state. Suspended mailboxes stop emitting events; inbound mail is retained as blocked. Possible values: `active`, `suspended` The channel this mailbox receives on. Always `email`. Possible values: `email` The principal that owns the mailbox. Always the workspace. Owner principal type. Possible values: `workspace` Owner principal ID. The underlying inbound address that receives this mailbox's mail. How long the mailbox remembers message metadata and extracted text. Original rendered source (HTML, raw message, attachments) is always available for 30 days regardless of tier. `3y` and `10y` are reserved future tiers. Possible values: `30d`, `90d`, `1y` Number of retained messages across all threads. Number of retained threads. Number of threads with unread messages in this mailbox, excluding trash. Null on create/update responses. Your own key/value data attached to the mailbox. Up to 2 KB; keys starting with `__bird` are reserved. Whether Bird generated the local part of the address. `false` means a custom handle was chosen at creation; on the shared `inbox.ai` domain a custom handle counts against your plan's custom-handle allowance. When the mailbox was created. When the mailbox was last updated. When the mailbox was deleted, or null if it is active. A deleted mailbox stops receiving mail immediately but can be restored for 30 days, after which it and its remembered messages are permanently removed.