Check if server support dsn before to force it

src/sendjob.cpp

@@ -170,7 +170,9 @@ void SendJob::handleResponse(const ServerResponse &r)
 
 void SendJobPrivate::sendNextRecipient()
 {
-    q->sendCommand("RCPT TO:<" + m_recipientsCopy.takeFirst().toUtf8() + '>' + (m_dsn ? " NOTIFY=success,failure" : ""));
+    const bool dnsSupport = m_session->allowsDns() ? m_dsn : false;
+    // qDebug() << " void SendJobPrivate::sendNextRecipient()" << m_session->allowsDns() << " dnsSupport " << dnsSupport;
+    q->sendCommand("RCPT TO:<" + m_recipientsCopy.takeFirst().toUtf8() + '>' + (dnsSupport ? " NOTIFY=success,failure" : ""));
 }
 
 void SendJobPrivate::addRecipients(const QStringList &rcpts)

src/session.cpp

@@ -149,6 +149,11 @@ bool Session::allowsTls() const
     return d->m_allowsTls;
 }
 
+bool Session::allowsDns() const
+{
+    return d->m_allowsDns;
+}
+
 QStringList Session::availableAuthModes() const
 {
     return d->m_authModes;
@@ -253,6 +258,8 @@ void SessionPrivate::responseReceived(const ServerResponse &r)
                 m_allowsTls = true;
             } else if (r.text().startsWith("AUTH ")) { // krazy:exclude=strings
                 setAuthenticationMethods(r.text().remove(0, QByteArray("AUTH ").count()).split(' '));
+            } else if (r.text() == "DSN") {
+                m_allowsDns = true;
             }
 
             if (!r.isMultiline()) {

src/session.h

@@ -93,6 +93,11 @@ public:
     */
     Q_REQUIRED_RESULT bool allowsTls() const;
 
+    /**
+      Returns true if the SMTP server has indicated that it allows DSN support, false otherwise.
+    */
+    Q_REQUIRED_RESULT bool allowsDns() const;
+
     /**
       @todo: return parsed auth modes, instead of strings.
     */

src/session_p.h

@@ -84,6 +84,7 @@ private:
     int m_size = 0;
     bool m_allowsTls = false;
     bool m_starttlsSent = false;
+    bool m_allowsDns = false;
     QStringList m_authModes;
     QString m_customHostname;
 };