fix(mail): align queue, outbound hostname, and DKIM selector behavior across the mail server APIs

readme.md

@@ -95,6 +95,8 @@ import { UnifiedEmailServer } from '@push.rocks/smartmta';
 const emailServer = new UnifiedEmailServer(dcRouterRef, {
   // Ports to listen on (465 = implicit TLS, 25/587 = STARTTLS)
   ports: [25, 587, 465],
+
+  // Public SMTP hostname used for greeting/banner and as the default outbound identity
   hostname: 'mail.example.com',
 
   // Multi-domain configuration
@@ -160,6 +162,16 @@ const emailServer = new UnifiedEmailServer(dcRouterRef, {
     keyPath: '/etc/ssl/mail.key',
   },
 
+  outbound: {
+    // Optional override for outbound EHLO/HELO identity
+    hostname: 'smtp-out.example.com',
+  },
+
+  queue: {
+    storageType: 'disk',
+    persistentPath: '/var/lib/smartmta/email-queue',
+  },
+
   maxMessageSize: 25 * 1024 * 1024, // 25 MB
   maxClients: 500,
 });
@@ -169,6 +181,8 @@ await emailServer.start();
 ```
 
 > 🔒 **Note:** `start()` will throw if the Rust binary is not compiled. Run `pnpm build` first.
+>
+> `hostname` is the public SMTP identity for greetings and outbound delivery by default. It is not a bind address.
 
 ### 📧 Sending Emails (Automatic MX Discovery)
 
@@ -201,6 +215,8 @@ const emailId = await emailServer.sendEmail(email);
 const emailId2 = await emailServer.sendEmail(email, 'mta');
 ```
 
+`sendEmail()` returns the delivery queue item ID, which you can later use with queue/status APIs.
+
 In MTA mode, smartmta:
 - 🔍 Resolves MX records for each recipient domain (e.g. `gmail.com`, `company.org`)
 - 📊 Sorts MX hosts by priority (lowest = highest priority per RFC 5321)
@@ -254,6 +270,7 @@ The `sendOutboundEmail` method:
 - 🔑 Automatically resolves DKIM keys from the `DKIMCreator` for the specified domain
 - 🔗 Uses connection pooling in Rust — reuses TCP/TLS connections across sends
 - ⏱️ Configurable connection and socket timeouts via `outbound` options on the server
+- 🪪 Uses `outbound.hostname` as the SMTP identity when configured, otherwise falls back to `hostname`
 
 ### 🔑 DKIM Signing & Key Management