diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 2b427cc..503b621 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -47,7 +47,7 @@ build_with_idf_v3:
 
 build_with_idf_v4:
   stage: build
-  image: ${CI_DOCKER_REGISTRY}/esp32-ci-env
+  image: ${CI_DOCKER_REGISTRY}/esp-env:v4.4-1
   tags:
     - build
   dependencies: []
@@ -56,9 +56,12 @@ build_with_idf_v4:
     paths:
       - tidybuild/*
     expire_in: 1 day
+  variables:
+    PYTHON_VER: 3.6.13
   script:
     - cit_add_ssh_key "${GITLAB_KEY}"
     - git clone "${IDF_REPO}"
+    - source /opt/pyenv/activate && pyenv global $PYTHON_VER
     - $MQTT_PATH/ci/set_idf.sh master
     - cd $IDF_PATH && tools/idf_tools.py --non-interactive install && eval "$(tools/idf_tools.py --non-interactive export)"
     - $MQTT_PATH/ci/set_mqtt.sh $CI_COMMIT_SHA
@@ -72,6 +75,11 @@ build_with_idf_v4:
     - export EXTRA_CFLAGS=${PEDANTIC_CFLAGS} && export EXTRA_CXXFLAGS=${EXTRA_CFLAGS}
     # build other examples
     - $MQTT_PATH/ci/build_examples.sh
+    # rebuild with IDFv4.3
+    - $MQTT_PATH/ci/set_idf.sh release/v4.3
+    - cd $IDF_PATH && tools/idf_tools.py --non-interactive install && eval "$(tools/idf_tools.py --non-interactive export)"
+    - $MQTT_PATH/ci/set_mqtt.sh $CI_COMMIT_SHA
+    - $MQTT_PATH/ci/build_examples.sh
     # rebuild with IDFv4.2
     - $MQTT_PATH/ci/set_idf.sh release/v4.2
     - cd $IDF_PATH && tools/idf_tools.py --non-interactive install && eval "$(tools/idf_tools.py --non-interactive export)"
@@ -90,26 +98,30 @@ build_with_idf_v4:
 
 build_and_test_qemu:
   stage: build
-  image: ${CI_DOCKER_REGISTRY}/qemu:esp-develop-20191124
+  image: ${CI_DOCKER_REGISTRY}/qemu:esp-develop-20210517-dda2caf0
   tags:
     - build
     - shiny
   dependencies: []
+  variables:
+    PYTHON_VER: 3.7.0
   script:
     - cit_add_ssh_key "${GITLAB_KEY}"
     - git clone "${IDF_REPO}"
-    - $MQTT_PATH/ci/set_idf.sh release/v4.1
+    # switch to IDF and setup the right tools
+    - $MQTT_PATH/ci/set_idf.sh master
+    - source /opt/pyenv/activate && pyenv install $PYTHON_VER && pyenv global $PYTHON_VER
     - cd $IDF_PATH && tools/idf_tools.py --non-interactive install && eval "$(tools/idf_tools.py --non-interactive export)"
+    - ./install.sh && source  export.sh
+    - python -m pip install -r $IDF_PATH/tools/ci/python_packages/ttfw_idf/requirements.txt && python -m pip install paho-mqtt
     - $MQTT_PATH/ci/set_mqtt.sh $CI_COMMIT_SHA
-    # build publish stress test
-    - cd $IDF_PATH/examples/protocols/mqtt/publish_test && cat sdkconfig.qemu | $IDF_PATH/tools/ci/envsubst.py >> sdkconfig.defaults && idf.py build
-    - source /opt/pyenv/activate && pyenv global 2.7.15 && python --version
-    # setup runner params
+    # build publish-connect stress test, setup test parameters
+    - cd tools/test_apps/protocols/mqtt/publish_connect_test && cat sdkconfig.qemu | $IDF_PATH/tools/ci/envsubst.py > sdkconfig.defaults && idf.py build
+    - export TEST_PATH=`pwd` && export MQTT_PUBLISH_TEST=1
     - export PYTHONPATH="$IDF_PATH/tools:$IDF_PATH/tools/ci/python_packages"
-    - export TEST_CASE_PATH=$IDF_PATH/components/mqtt/weekend_test
-    - cd $IDF_PATH/tools/ci/python_packages/tiny_test_fw/bin
     # run test (with environment->qemu)
-    - python Runner.py $TEST_CASE_PATH -c $TEST_CASE_PATH/test_weekend_mqtt_qemu.yml -e $TEST_CASE_PATH/env.yml
+    - cd $IDF_PATH/tools/ci/python_packages/tiny_test_fw/bin
+    - python Runner.py $TEST_PATH -c $TEST_PATH/publish_connect_mqtt_qemu.yml -e $TEST_PATH/env.yml
 
 clang_tidy_check:
   stage: static_analysis
diff --git a/include/mqtt_supported_features.h b/include/mqtt_supported_features.h
index eaad295..6e49182 100644
--- a/include/mqtt_supported_features.h
+++ b/include/mqtt_supported_features.h
@@ -57,6 +57,10 @@
 // Features supported in 4.3
 #define MQTT_SUPPORTED_FEATURE_DIGITAL_SIGNATURE
 #define MQTT_SUPPORTED_FEATURE_TRANSPORT_SOCK_ERRNO_REPORTING
+#endif
+
+#if ESP_IDF_VERSION >= ESP_IDF_VERSION_VAL(4, 4, 0)
+// Features supported in 4.4
 #define MQTT_SUPPORTED_FEATURE_CERTIFICATE_BUNDLE
 #endif
 
diff --git a/lib/include/mqtt_outbox.h b/lib/include/mqtt_outbox.h
index 21a10dd..7010e39 100644
--- a/lib/include/mqtt_outbox.h
+++ b/lib/include/mqtt_outbox.h
@@ -58,6 +58,7 @@ esp_err_t outbox_set_tick(outbox_handle_t outbox, int msg_id, outbox_tick_t tick
 int outbox_get_size(outbox_handle_t outbox);
 esp_err_t outbox_cleanup(outbox_handle_t outbox, int max_size);
 void outbox_destroy(outbox_handle_t outbox);
+void outbox_delete_all_items(outbox_handle_t outbox);
 
 #ifdef  __cplusplus
 }
diff --git a/lib/mqtt_outbox.c b/lib/mqtt_outbox.c
index 77ef3ec..e6fc12b 100644
--- a/lib/mqtt_outbox.c
+++ b/lib/mqtt_outbox.c
@@ -224,7 +224,7 @@ esp_err_t outbox_cleanup(outbox_handle_t outbox, int max_size)
     return ESP_OK;
 }
 
-void outbox_destroy(outbox_handle_t outbox)
+void outbox_delete_all_items(outbox_handle_t outbox)
 {
     outbox_item_handle_t item, tmp;
     STAILQ_FOREACH_SAFE(item, outbox, next, tmp) {
@@ -232,6 +232,10 @@ void outbox_destroy(outbox_handle_t outbox)
         free(item->buffer);
         free(item);
     }
+}
+void outbox_destroy(outbox_handle_t outbox)
+{
+    outbox_delete_all_items(outbox);
     free(outbox);
 }
 
diff --git a/mqtt_client.c b/mqtt_client.c
index 14d91ea..f015de9 100644
--- a/mqtt_client.c
+++ b/mqtt_client.c
@@ -1491,6 +1491,7 @@ static void esp_mqtt_task(void *pv)
 
     }
     esp_transport_close(client->transport);
+    outbox_delete_all_items(client->outbox);
     xEventGroupSetBits(client->status_bits, STOPPED_BIT);
 
     vTaskDelete(NULL);