smtp_proxy: handle dead sender more gracefully (#3286)

* q/proxy: check client is alive b4 sending cmd

docs/plugins/queue/smtp_proxy.md

@@ -1,16 +1,11 @@
 # queue/smtp\_proxy
 ================
 
-This plugin delivers to another mail server. This is a common setup when you
-want to have a mail server with a solid pedigree of outbound delivery to
-other hosts, and inbound delivery to users.
-
-In comparison to `queue/smtp_forward`, this plugin makes a connection at
-MAIL FROM time to the ongoing SMTP server. This can be a benefit in that
-you get any SMTP-time filtering that the ongoing server provides, in
-particular one important facility to some setups is recipient filtering.
-However be aware that other than connect and HELO-time filtering, you will
-have as many connections to your ongoing SMTP server as you have to Haraka.
+This plugin delivers to another mail server. This is a common setup when you want to have a mail server with a solid pedigree of outbound delivery to other hosts, and inbound delivery to users.
+
+In comparison to `queue/smtp_forward`, this plugin makes a connection at MAIL FROM time to the ongoing SMTP server. This can be a benefit in that you get any SMTP-time filtering that the ongoing server provides, in particular one important facility to some setups is recipient filtering.
+
+Be aware that other than connect and HELO-time filtering, you will have as many connections to your ongoing SMTP server as you have to Haraka.
 
 ## Configuration
 -------------

plugins/queue/smtp_forward.js

@@ -247,8 +247,7 @@ exports.queue_forward = function (next, connection) {
         );
 
         function get_rs () {
-            if (txn) return txn.results;
-            return connection.results;
+            return connection?.transaction?.results ? connection.transaction.results : connection.results
         }
 
         function dead_sender () {

plugins/queue/smtp_proxy.js

@@ -79,13 +79,22 @@ exports.hook_mail = function (next, connection, params) {
 exports.hook_rcpt_ok = (next, connection, recipient) => {
     const { smtp_client } = connection.notes;
     if (!smtp_client) return next();
+    if (smtp_client.is_dead_sender(this, connection)) {
+        delete connection.notes.smtp_client;
+        return;
+    }
     smtp_client.next = next;
     smtp_client.send_command('RCPT', `TO:${recipient.format(!smtp_client.smtp_utf8)}`);
 }
 
 exports.hook_data = (next, connection) => {
     const { smtp_client } = connection.notes;
     if (!smtp_client) return next();
+
+    if (smtp_client.is_dead_sender(this, connection)) {
+        delete connection.notes.smtp_client;
+        return;
+    }
     smtp_client.next = next;
     smtp_client.send_command("DATA");
 }
@@ -96,11 +105,11 @@ exports.hook_queue = function (next, connection) {
     const { smtp_client } = connection.notes;
     if (!smtp_client) return next();
 
-    smtp_client.next = next;
     if (smtp_client.is_dead_sender(this, connection)) {
         delete connection.notes.smtp_client;
         return;
     }
+    smtp_client.next = next;
     smtp_client.start_data(connection.transaction.message_stream);
 }