diff --git a/.DS_Store b/.DS_Store
new file mode 100644
index 0000000..24480c3
Binary files /dev/null and b/.DS_Store differ
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 8d412a8..8ef223d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,6 +6,14 @@ The format follows [Keep a Changelog](https://keepachangelog.com/en/1.1.0/). Thi
 
 ---
 
+## [Unreleased]
+
+### Added
+
+- `openmail inbox create` and `openmail init` accept `--domain <domain>` to create an inbox on a verified custom domain you own. When omitted, the inbox uses your account default domain.
+
+---
+
 ## [0.1.6] — current
 
 Initial public release on [openmailsh/cli](https://github.com/openmailsh/cli).
diff --git a/README.md b/README.md
index 1a75eef..f91ede9 100644
--- a/README.md
+++ b/README.md
@@ -36,11 +36,11 @@ openmail setup [--mode websocket|webhook]
 
 ```bash
 # Create a new inbox (interactive prompts, or pass flags)
-openmail init [--mailbox-name john] [--display-name "John Smith"]
+openmail init [--mailbox-name john] [--display-name "John Smith"] [--domain agent-mail.example.com]
 
 # Manage inboxes
 openmail inbox list --limit 10
-openmail inbox create [--mailbox-name <name>] [--display-name <sender name>]
+openmail inbox create [--mailbox-name <name>] [--display-name <sender name>] [--domain <domain>]
 openmail inbox get --id inb_xxx
 openmail inbox delete --id inb_xxx
 
diff --git a/src/commands/__tests__/inbox.test.ts b/src/commands/__tests__/inbox.test.ts
new file mode 100644
index 0000000..ab52cfc
--- /dev/null
+++ b/src/commands/__tests__/inbox.test.ts
@@ -0,0 +1,51 @@
+import { describe, expect, it, vi } from "vitest";
+import { parseArgs } from "../../lib/args";
+import { runInboxCommand } from "../inbox";
+import type { OpenMailHttpClient } from "../../lib/http";
+
+function makeClient() {
+  return {
+    post: vi.fn().mockResolvedValue({ id: "inb_1", address: "support@yourco.com" }),
+    get: vi.fn().mockResolvedValue({ data: [], total: 0 }),
+    delete: vi.fn().mockResolvedValue({ ok: true }),
+  } as unknown as OpenMailHttpClient & {
+    post: ReturnType<typeof vi.fn>;
+    get: ReturnType<typeof vi.fn>;
+    delete: ReturnType<typeof vi.fn>;
+  };
+}
+
+describe("runInboxCommand create", () => {
+  it("forwards --domain to POST /v1/inboxes", async () => {
+    const client = makeClient();
+    const parsed = parseArgs([
+      "inbox",
+      "create",
+      "--mailbox-name",
+      "support",
+      "--display-name",
+      "Support",
+      "--domain",
+      "agent-mail.example.com",
+    ]);
+
+    await runInboxCommand(client, parsed);
+
+    expect(client.post).toHaveBeenCalledWith("/v1/inboxes", {
+      mailboxName: "support",
+      displayName: "Support",
+      domain: "agent-mail.example.com",
+    });
+  });
+
+  it("omits domain when the flag is not provided", async () => {
+    const client = makeClient();
+    const parsed = parseArgs(["inbox", "create", "--mailbox-name", "support"]);
+
+    await runInboxCommand(client, parsed);
+
+    expect(client.post).toHaveBeenCalledWith("/v1/inboxes", {
+      mailboxName: "support",
+    });
+  });
+});
diff --git a/src/commands/inbox.ts b/src/commands/inbox.ts
index 3906e9d..aeeef70 100644
--- a/src/commands/inbox.ts
+++ b/src/commands/inbox.ts
@@ -11,9 +11,11 @@ export async function runInboxCommand(client: OpenMailHttpClient, parsed: Parsed
   if (action === "create") {
     const mailboxName = getStringFlag(parsed.flags, "mailbox-name");
     const displayName = getStringFlag(parsed.flags, "display-name");
+    const domain = getStringFlag(parsed.flags, "domain");
     return client.post("/v1/inboxes", {
       ...(mailboxName ? { mailboxName } : {}),
       ...(displayName ? { displayName } : {}),
+      ...(domain ? { domain } : {}),
     });
   }
 
diff --git a/src/commands/init.ts b/src/commands/init.ts
index dc7f35b..ea55383 100644
--- a/src/commands/init.ts
+++ b/src/commands/init.ts
@@ -20,10 +20,12 @@ export async function runInitCommand(params: {
 }) {
   const mailboxName = getStringFlag(params.parsed.flags, "mailbox-name");
   const displayName = getStringFlag(params.parsed.flags, "display-name");
+  const domain = getStringFlag(params.parsed.flags, "domain");
 
   const createParams = await resolveInboxCreateParams({
     mailboxName,
     displayName,
+    domain,
     ctx: params.ctx,
     cancelMessage: "Init cancelled.",
   });
diff --git a/src/index.ts b/src/index.ts
index bffc380..68f379d 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -280,9 +280,9 @@ function printHelp(topic?: string) {
         "openmail init",
         "",
         "Usage:",
-        "  init [--mailbox-name <name>] [--display-name <sender name>]",
+        "  init [--mailbox-name <name>] [--display-name <sender name>] [--domain <domain>]",
         "",
-        "Creates a new inbox and sets it as the default. Prompts interactively for mailbox name and display name when run without flags.",
+        "Creates a new inbox and sets it as the default. Prompts interactively for mailbox name and display name when run without flags. Pass --domain to create the inbox on a verified custom domain.",
         "",
         ...globalFlags,
       ].join("\n"),
@@ -344,11 +344,15 @@ function printHelp(topic?: string) {
         "openmail inbox",
         "",
         "Subcommands:",
-        "  create [--mailbox-name <name>] [--display-name <sender name>]",
+        "  create [--mailbox-name <name>] [--display-name <sender name>] [--domain <domain>]",
         "  list [--limit <n>] [--offset <n>]",
         "  get --id <inbox_id>",
         "  delete --id <inbox_id>",
         "",
+        "Notes:",
+        "  --domain  Create the inbox on a verified custom domain you own",
+        "            (defaults to your account domain when omitted).",
+        "",
         ...globalFlags,
       ].join("\n"),
     );
diff --git a/src/lib/inbox-create.ts b/src/lib/inbox-create.ts
index 4ec65eb..dda66d9 100644
--- a/src/lib/inbox-create.ts
+++ b/src/lib/inbox-create.ts
@@ -6,13 +6,15 @@ export const MAILBOX_NAME_REGEX = /^[a-z0-9][a-z0-9.\-]{1,28}[a-z0-9]$/;
 export async function resolveInboxCreateParams(params: {
   mailboxName?: string;
   displayName?: string;
+  domain?: string;
   ctx: CliContext;
   cancelMessage?: string;
-}): Promise<{ mailboxName?: string; displayName?: string }> {
-  if (params.mailboxName || params.displayName) {
+}): Promise<{ mailboxName?: string; displayName?: string; domain?: string }> {
+  if (params.mailboxName || params.displayName || params.domain) {
     return {
       ...(params.mailboxName ? { mailboxName: params.mailboxName } : {}),
       ...(params.displayName ? { displayName: params.displayName } : {}),
+      ...(params.domain ? { domain: params.domain } : {}),
     };
   }