diff --git a/tests/drivers/mbox/mbox_error_cases/CMakeLists.txt b/tests/drivers/mbox/mbox_error_cases/CMakeLists.txt
new file mode 100644
index 00000000000..13d801e7fe9
--- /dev/null
+++ b/tests/drivers/mbox/mbox_error_cases/CMakeLists.txt
@@ -0,0 +1,11 @@
+#
+# Copyright 2024 Nordic Semiconductor ASA
+# SPDX-License-Identifier: Apache-2.0
+#
+
+cmake_minimum_required(VERSION 3.20.0)
+
+find_package(Zephyr REQUIRED HINTS $ENV{ZEPHYR_BASE})
+project(mbox_error_cases)
+
+target_sources(app PRIVATE src/main.c)
diff --git a/tests/drivers/mbox/mbox_error_cases/boards/nrf54h20dk_nrf54h20_cpuapp.overlay b/tests/drivers/mbox/mbox_error_cases/boards/nrf54h20dk_nrf54h20_cpuapp.overlay
new file mode 100644
index 00000000000..84006d1d435
--- /dev/null
+++ b/tests/drivers/mbox/mbox_error_cases/boards/nrf54h20dk_nrf54h20_cpuapp.overlay
@@ -0,0 +1,22 @@
+/*
+ * Copyright 2024 Nordic Semiconductor ASA
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/ {
+	mbox-consumer {
+		compatible = "vnd,mbox-consumer";
+		mboxes = <&cpuppr_vevif 15>, <&cpuppr_vevif 32>,
+				 <&cpuapp_bellboard 18>, <&cpuapp_bellboard 32>;
+		mbox-names = "remote_valid", "remote_incorrect",
+					 "local_valid", "local_incorrect";
+	};
+};
+
+&cpuapp_bellboard {
+	status = "okay";
+};
+
+&cpuppr_vevif {
+	status = "okay";
+};
diff --git a/tests/drivers/mbox/mbox_error_cases/boards/nrf54h20dk_nrf54h20_cpuppr.overlay b/tests/drivers/mbox/mbox_error_cases/boards/nrf54h20dk_nrf54h20_cpuppr.overlay
new file mode 100644
index 00000000000..b39bd5e4962
--- /dev/null
+++ b/tests/drivers/mbox/mbox_error_cases/boards/nrf54h20dk_nrf54h20_cpuppr.overlay
@@ -0,0 +1,22 @@
+/*
+ * Copyright 2024 Nordic Semiconductor ASA
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/ {
+	mbox-consumer {
+		compatible = "vnd,mbox-consumer";
+		mboxes = <&cpuapp_bellboard 18>, <&cpuapp_bellboard 32>,
+				 <&cpuppr_vevif 15>, <&cpuppr_vevif 32>;
+		mbox-names = "remote_valid", "remote_incorrect",
+					 "local_valid", "local_incorrect";
+	};
+};
+
+&cpuapp_bellboard {
+	status = "okay";
+};
+
+&cpuppr_vevif {
+	status = "okay";
+};
diff --git a/tests/drivers/mbox/mbox_error_cases/prj.conf b/tests/drivers/mbox/mbox_error_cases/prj.conf
new file mode 100644
index 00000000000..d27f609b89d
--- /dev/null
+++ b/tests/drivers/mbox/mbox_error_cases/prj.conf
@@ -0,0 +1,3 @@
+CONFIG_ZTEST=y
+
+CONFIG_MBOX=y
diff --git a/tests/drivers/mbox/mbox_error_cases/sample.yaml b/tests/drivers/mbox/mbox_error_cases/sample.yaml
new file mode 100644
index 00000000000..93f64dcd478
--- /dev/null
+++ b/tests/drivers/mbox/mbox_error_cases/sample.yaml
@@ -0,0 +1,13 @@
+sample:
+  name: MBOX IPC negative test cases
+common:
+  tags: drivers mbox
+  harness: ztest
+tests:
+
+  tests.drivers.mbox_error_cases:
+    platform_allow:
+      - nrf54h20dk/nrf54h20/cpuapp
+      - nrf54h20dk/nrf54h20/cpuppr
+    integration_platforms:
+      - nrf54h20dk/nrf54h20/cpuapp
diff --git a/tests/drivers/mbox/mbox_error_cases/src/main.c b/tests/drivers/mbox/mbox_error_cases/src/main.c
new file mode 100644
index 00000000000..81eb3e656a7
--- /dev/null
+++ b/tests/drivers/mbox/mbox_error_cases/src/main.c
@@ -0,0 +1,576 @@
+/*
+ * Copyright (c) 2024, Nordic Semiconductor ASA
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <zephyr/kernel.h>
+#include <zephyr/ztest.h>
+#include <zephyr/drivers/mbox.h>
+
+int dummy_value;
+
+#if defined(CONFIG_SOC_NRF54L15) || defined(CONFIG_SOC_NRF54H20)
+#define EXPECTED_MTU_VALUE				(0)
+#define DATA_TRANSFER_MODE_SUPPORTED	(0)
+#define REMOTE_BUSY_SUPPORTED			(0)
+#else
+#define EXPECTED_MTU_VALUE				(4)
+#define DATA_TRANSFER_MODE_SUPPORTED	(1)
+#define REMOTE_BUSY_SUPPORTED			(1)
+#endif
+
+static void dummy_callback(const struct device *dev, mbox_channel_id_t channel_id,
+		     void *user_data, struct mbox_msg *data)
+{
+	ARG_UNUSED(dev);
+	ARG_UNUSED(channel_id);
+	ARG_UNUSED(user_data);
+	ARG_UNUSED(data);
+	/* Nothing here */
+}
+
+static void dummy_callback_2(const struct device *dev, mbox_channel_id_t channel_id,
+		     void *user_data, struct mbox_msg *data)
+{
+	ARG_UNUSED(dev);
+	ARG_UNUSED(channel_id);
+	ARG_UNUSED(data);
+
+	int *temp = (int *) user_data;
+	(*temp)++;
+}
+
+/**
+ * @brief mbox_is_ready_dt() positive test
+ *
+ * Confirm that mbox_is_ready_dt() returns True
+ * on valid local and remote mbox channels.
+ *
+ */
+ZTEST(mbox_error_cases, test_01a_mbox_is_ready_positive)
+{
+	const struct mbox_dt_spec rx_channel =
+		MBOX_DT_SPEC_GET(DT_PATH(mbox_consumer), local_valid);
+	const struct mbox_dt_spec tx_channel =
+		MBOX_DT_SPEC_GET(DT_PATH(mbox_consumer), remote_valid);
+	bool ret;
+
+	ret = mbox_is_ready_dt(&tx_channel);
+	zassert_true(
+		ret,
+		"mbox_is_ready_dt(tx_channel) should return True,"
+		" got unexpected value of %d",
+		ret
+	);
+
+	ret = mbox_is_ready_dt(&rx_channel);
+	zassert_true(
+		ret,
+		"mbox_is_ready_dt(rx_channel) should return True,"
+		" got unexpected value of %d",
+		ret
+	);
+}
+
+/**
+ * @brief mbox_is_ready_dt() on incorrect channels
+ *
+ * Confirm that mbox_is_ready_dt() returns True
+ * on invalid local and remote mbox channel.
+ * (Device is ready, channel is not checked.)
+ *
+ */
+ZTEST(mbox_error_cases, test_01b_mbox_is_ready_negative)
+{
+	const struct mbox_dt_spec rx_channel =
+		MBOX_DT_SPEC_GET(DT_PATH(mbox_consumer), local_incorrect);
+	const struct mbox_dt_spec tx_channel =
+		MBOX_DT_SPEC_GET(DT_PATH(mbox_consumer), remote_incorrect);
+	bool ret;
+
+	ret = mbox_is_ready_dt(&tx_channel);
+	zassert_true(
+		ret,
+		"mbox_is_ready_dt(tx_invalid_channel) should return True,"
+		" got unexpected value of %d",
+		ret
+	);
+
+	ret = mbox_is_ready_dt(&rx_channel);
+	zassert_true(
+		ret,
+		"mbox_is_ready_dt(rx_invalid_channel) should return True,"
+		" got unexpected value of %d", ret
+	);
+}
+
+/**
+ * @brief mbox_send_dt() on invalid TX channel shall fail
+ *
+ * Confirm that mbox_send_dt() returns
+ * -EINVAL when TX channel is invalid.
+ *
+ */
+ZTEST(mbox_error_cases, test_02a_mbox_send_on_invalid_tx_channel)
+{
+	const struct mbox_dt_spec tx_channel =
+		MBOX_DT_SPEC_GET(DT_PATH(mbox_consumer), remote_incorrect);
+	int ret;
+
+	ret = mbox_send_dt(&tx_channel, NULL);
+	zassert_true(
+		(ret == -EINVAL),
+		"mbox_send_dt(incorrect_tx_channel) shall return -EINVAL (-22)"
+		" got unexpected %d",
+		ret
+	);
+}
+
+/**
+ * @brief mbox_send_dt() on RX channel shall fail
+ *
+ * Confirm that mbox_send_dt() returns
+ * -ENOSYS when user tries to send on RX channel.
+ *
+ */
+ZTEST(mbox_error_cases, test_02b_mbox_send_on_rx_channel)
+{
+	const struct mbox_dt_spec rx_channel =
+		MBOX_DT_SPEC_GET(DT_PATH(mbox_consumer), local_valid);
+	int ret;
+
+	ret = mbox_send_dt(&rx_channel, NULL);
+	zassert_true(
+		(ret == -ENOSYS),
+		"mbox_send_dt(rx_channel) shall return -ENOSYS (-88)"
+		" got unexpected %d",
+		ret
+	);
+}
+
+/**
+ * @brief mbox_send_dt() with nonzero data field
+ *
+ * Confirm that mbox_send_dt() returns
+ * -EMSGSIZE when driver does NOT support DATA transfer.
+ *
+ */
+ZTEST(mbox_error_cases, test_02c_mbox_send_message_with_data)
+{
+	const struct mbox_dt_spec tx_channel =
+		MBOX_DT_SPEC_GET(DT_PATH(mbox_consumer), remote_valid);
+	struct mbox_msg data_msg = {0};
+	int ret;
+
+	if (DATA_TRANSFER_MODE_SUPPORTED) {
+		/* Skip this test because data transfer is supported. */
+		ztest_test_skip();
+	}
+
+	data_msg.data = &dummy_value;
+	data_msg.size = 4;
+
+	ret = mbox_send_dt(&tx_channel, &data_msg);
+	zassert_true(
+		(ret == -EMSGSIZE),
+		"mbox_send_dt(rx_channel, data) shall return -EMSGSIZE (-122)"
+		" got unexpected %d",
+		ret
+	);
+}
+
+/**
+ * @brief mbox_send_dt() remote busy
+ *
+ * Confirm that mbox_send_dt() returns
+ * -EBUSY when remote hasn’t yet read the last data sent.
+ *
+ */
+ZTEST(mbox_error_cases, test_02d_mbox_send_message_remote_busy)
+{
+	const struct mbox_dt_spec tx_channel =
+		MBOX_DT_SPEC_GET(DT_PATH(mbox_consumer), remote_valid);
+	int ret;
+
+	if (!REMOTE_BUSY_SUPPORTED)	{
+		/* Skip this test because driver is not
+		 * capable of detecting that remote is busy.
+		 */
+		ztest_test_skip();
+	}
+
+	ret = mbox_send_dt(&tx_channel, NULL);
+	zassert_true(
+		(ret == 0),
+		"mbox_send_dt(rx_channel) shall return 0"
+		" got unexpected %d",
+		ret
+	);
+
+	ret = mbox_send_dt(&tx_channel, NULL);
+	zassert_true(
+		(ret == -EBUSY),
+		"mbox_send_dt(rx_channel) shall return -EBUSY (-16)"
+		" got unexpected %d",
+		ret
+	);
+}
+
+/**
+ * @brief mbox_register_callback_dt() on TX channel shall fail
+ *
+ * Confirm that mbox_register_callback_dt() returns
+ * -ENOSYS when user tries to register callback on TX mbox channel.
+ *
+ */
+ZTEST(mbox_error_cases, test_03a_mbox_register_callback_on_remote_channel)
+{
+	const struct mbox_dt_spec tx_channel =
+		MBOX_DT_SPEC_GET(DT_PATH(mbox_consumer), remote_valid);
+	int ret;
+
+	ret = mbox_register_callback_dt(&tx_channel, dummy_callback, NULL);
+	zassert_true(
+		(ret == -ENOSYS),
+		"mbox_register_callback(remote_channel) shall return -ENOSYS (-88)"
+		" got unexpected %d",
+		ret
+	);
+}
+
+/**
+ * @brief mbox_register_callback_dt() on incorrect channel shall fail
+ *
+ * Confirm that mbox_register_callback_dt() returns
+ * -EINVAL when user tries to register callback on incorrect mbox channel.
+ *
+ */
+ZTEST(mbox_error_cases, test_03b_mbox_register_callback_on_invalid_channel)
+{
+	const struct mbox_dt_spec rx_channel =
+		MBOX_DT_SPEC_GET(DT_PATH(mbox_consumer), local_incorrect);
+	int ret;
+
+	ret = mbox_register_callback_dt(&rx_channel, dummy_callback, NULL);
+	zassert_true(
+		(ret == -EINVAL),
+		"mbox_register_callback(incorrect_channel) shall return -EINVAL (-22)"
+		" got unexpected %d",
+		ret
+	);
+}
+
+/**
+ * @brief mbox_register_callback_dt() multiple use on same channel
+ *
+ * Confirm that mbox_register_callback_dt() returns
+ * 0 when user tries to register callback
+ * on already configured mbox channel.
+ *
+ */
+ZTEST(mbox_error_cases, test_03c_mbox_register_callback_twice_on_same_channel)
+{
+	const struct mbox_dt_spec rx_channel =
+		MBOX_DT_SPEC_GET(DT_PATH(mbox_consumer), local_valid);
+	int ret;
+
+	ret = mbox_register_callback_dt(&rx_channel, dummy_callback, NULL);
+	zassert_true(
+		(ret == 0),
+		"mbox_register_callback(valid_channel) shall return 0"
+		" got unexpected %d",
+		ret
+	);
+
+	ret = mbox_register_callback_dt(&rx_channel, dummy_callback_2, &dummy_value);
+	zassert_true(
+		(ret == 0),
+		"mbox_register_callback(valid_channel) shall return 0"
+		" got unexpected %d",
+		ret
+	);
+}
+
+/**
+ * @brief mbox_mtu_get_dt() on RX channel shall fail
+ *
+ * Confirm that mbox_mtu_get_dt() returns
+ * -ENOSYS for RX mbox channel.
+ *
+ */
+ZTEST(mbox_error_cases, test_04a_mbox_mtu_get_on_rx_channel)
+{
+	const struct mbox_dt_spec rx_channel =
+		MBOX_DT_SPEC_GET(DT_PATH(mbox_consumer), local_valid);
+	int ret;
+
+	ret = mbox_mtu_get_dt(&rx_channel);
+	zassert_true(
+		(ret == -ENOSYS),
+		"mbox_mtu_get_dt(rx_channel) shall return -ENOSYS (-88)"
+		" got unexpected %d",
+		ret
+	);
+}
+
+/**
+ * @brief mbox_mtu_get_dt() on TX channel functional test
+ *
+ * Confirm that mbox_mtu_get_dt() returns
+ * expected value for TX mbox channel.
+ * (No matter if channel is valid or incorrect.)
+ *
+ */
+ZTEST(mbox_error_cases, test_04b_mbox_mtu_get_on_tx_channel)
+{
+	const struct mbox_dt_spec tx_channel =
+		MBOX_DT_SPEC_GET(DT_PATH(mbox_consumer), remote_valid);
+	const struct mbox_dt_spec tx_channel_incorrect =
+		MBOX_DT_SPEC_GET(DT_PATH(mbox_consumer), remote_incorrect);
+	int ret;
+
+	ret = mbox_mtu_get_dt(&tx_channel);
+	zassert_true(
+		(ret == EXPECTED_MTU_VALUE),
+		"mbox_mtu_get_dt(tx_channel) shall return %d"
+		" got unexpected %d",
+		EXPECTED_MTU_VALUE,
+		ret
+	);
+
+	ret = mbox_mtu_get_dt(&tx_channel_incorrect);
+	zassert_true(
+		(ret == EXPECTED_MTU_VALUE),
+		"mbox_mtu_get_dt(tx_channel_incorrect) shall return %d"
+		" got unexpected %d",
+		EXPECTED_MTU_VALUE,
+		ret
+	);
+}
+
+/**
+ * @brief mbox_set_enabled_dt() - Enable TX channel shall fail
+ *
+ * Confirm that mbox_set_enabled_dt() returns
+ * -ENOSYS for TX mbox channel.
+ *
+ */
+ZTEST(mbox_error_cases, test_05a_mbox_set_enabled_on_tx_channel)
+{
+	const struct mbox_dt_spec tx_channel =
+		MBOX_DT_SPEC_GET(DT_PATH(mbox_consumer), remote_valid);
+	int ret;
+
+	ret = mbox_set_enabled_dt(&tx_channel, true);
+	zassert_true(
+		(ret == -ENOSYS),
+		"mbox_set_enabled_dt(tx_channel, true) shall return -ENOSYS (-88)"
+		" got unexpected %d",
+		ret
+	);
+}
+
+/**
+ * @brief mbox_set_enabled_dt() - Enable incorrect channel shall fail
+ *
+ * Confirm that mbox_set_enabled_dt() returns
+ * -EINVAL for incorrect RX mbox channel.
+ *
+ */
+ZTEST(mbox_error_cases, test_05b_mbox_set_enabled_on_incorrect_rx_channel)
+{
+	const struct mbox_dt_spec rx_channel =
+		MBOX_DT_SPEC_GET(DT_PATH(mbox_consumer), local_incorrect);
+	int ret;
+
+	ret = mbox_set_enabled_dt(&rx_channel, true);
+	zassert_true(
+		(ret == -EINVAL),
+		"mbox_set_enabled_dt(incorrect_channel, true) shall return -EINVAL (-22)"
+		" got unexpected %d",
+		ret
+	);
+}
+
+/**
+ * @brief mbox_set_enabled_dt() - Enable already enabled channel shall fail
+ *
+ * Confirm that mbox_set_enabled_dt() returns
+ * -EALREADY when user tries to enable already enabled RX mbox channel.
+ *
+ */
+ZTEST(mbox_error_cases, test_05c_mbox_set_enabled_on_already_enabled_rx_channel)
+{
+	const struct mbox_dt_spec rx_channel =
+		MBOX_DT_SPEC_GET(DT_PATH(mbox_consumer), local_valid);
+	int ret;
+
+	/* The user must take care of installing a proper callback
+	 * on the channel before enabling it.
+	 */
+	ret = mbox_register_callback_dt(&rx_channel, dummy_callback, NULL);
+	zassert_true(
+		(ret == 0),
+		"mbox_register_callback(tx_channel) shall return 0"
+		" got unexpected %d",
+		ret
+	);
+
+	ret = mbox_set_enabled_dt(&rx_channel, true);
+	zassert_true(
+		(ret == 0),
+		"mbox_set_enabled_dt(tx_channel, true) shall return 0"
+		" got unexpected %d",
+		ret
+	);
+
+	ret = mbox_set_enabled_dt(&rx_channel, true);
+	zassert_true(
+		(ret == -EALREADY),
+		"mbox_set_enabled_dt(enabled_tx_channel, true) shall return -EALREADY (-120)"
+		" got unexpected %d",
+		ret
+	);
+
+	/* Cleanup - disable mbox channel */
+	ret = mbox_set_enabled_dt(&rx_channel, false);
+	zassert_true(
+		(ret == 0),
+		"mbox_set_enabled_dt(enabled_tx_channel, false) shall return 0"
+		" got unexpected %d",
+		ret
+	);
+}
+
+/**
+ * @brief mbox_set_enabled_dt() - Dsiable already disabled channel shall fail
+ *
+ * Confirm that mbox_set_enabled_dt() returns
+ * -EALREADY when user tries to disable already disabled RX mbox channel.
+ *
+ */
+ZTEST(mbox_error_cases, test_05d_mbox_set_enabled_on_already_disabled_rx_channel)
+{
+	const struct mbox_dt_spec rx_channel =
+		MBOX_DT_SPEC_GET(DT_PATH(mbox_consumer), local_valid);
+	int ret;
+
+	/* The user must take care of installing a proper callback
+	 * on the channel before enabling it.
+	 */
+	ret = mbox_register_callback_dt(&rx_channel, dummy_callback, NULL);
+	zassert_true(
+		(ret == 0),
+		"mbox_register_callback(tx_channel) shall return 0"
+		" got unexpected %d",
+		ret
+	);
+
+	ret = mbox_set_enabled_dt(&rx_channel, true);
+	zassert_true(
+		(ret == 0),
+		"mbox_set_enabled_dt(tx_channel, true) shall return 0"
+		" got unexpected %d",
+		ret
+	);
+
+	ret = mbox_set_enabled_dt(&rx_channel, false);
+	zassert_true(
+		(ret == 0),
+		"mbox_set_enabled_dt(enabled_tx_channel, false) shall return 0"
+		" got unexpected %d",
+		ret
+	);
+
+	ret = mbox_set_enabled_dt(&rx_channel, false);
+	zassert_true(
+		(ret == -EALREADY),
+		"mbox_set_enabled_dt(disabled_tx_channel, false) shall return -EALREADY (-120)"
+		" got unexpected %d",
+		ret
+	);
+}
+
+/**
+ * @brief mbox_max_channels_get_dt() functional test
+ *
+ * Confirm that mbox_max_channels_get_dt() returns
+ * >0 Maximum possible number of supported channels on success
+ * (No matter if channel is valid or incorrect.)
+ *
+ */
+ZTEST(mbox_error_cases, test_06_mbox_max_channels_get_functional)
+{
+	const struct mbox_dt_spec tx_channel =
+		MBOX_DT_SPEC_GET(DT_PATH(mbox_consumer), remote_valid);
+	const struct mbox_dt_spec tx_channel_incorrect =
+		MBOX_DT_SPEC_GET(DT_PATH(mbox_consumer), remote_incorrect);
+	const struct mbox_dt_spec rx_channel =
+		MBOX_DT_SPEC_GET(DT_PATH(mbox_consumer), local_valid);
+	const struct mbox_dt_spec rx_channel_incorrect =
+		MBOX_DT_SPEC_GET(DT_PATH(mbox_consumer), local_incorrect);
+	int ret1, ret2;
+
+	ret1 = mbox_max_channels_get_dt(&tx_channel);
+	TC_PRINT("mbox_max_channels_get_dt(tx_channel): %d\n", ret1);
+	zassert_true(
+		(ret1 > 0),
+		"mbox_max_channels_get_dt(tx_channel) shall return value greater than 0"
+		" got unexpected %d",
+		ret1
+	);
+
+	ret2 = mbox_max_channels_get_dt(&tx_channel_incorrect);
+	TC_PRINT("mbox_max_channels_get_dt(tx_channel_incorrect): %d\n", ret2);
+	zassert_true(
+		(ret2 > 0),
+		"mbox_max_channels_get_dt(tx_channel_incorrect) shall return value greater than 0"
+		" got unexpected %d",
+		ret2
+	);
+
+	zassert_true(
+		(ret1 == ret2),
+		"mbox_max_channels_get_dt() shall return same value disregarding channel No."
+		" got unexpected %d and %d",
+		ret1,
+		ret2
+	);
+
+	ret1 = mbox_max_channels_get_dt(&rx_channel);
+	TC_PRINT("mbox_max_channels_get_dt(rx_channel): %d\n", ret1);
+	zassert_true(
+		(ret1 > 0),
+		"mbox_max_channels_get_dt(rx_channel) shall return value greater than 0"
+		" got unexpected %d",
+		ret1
+	);
+
+	ret2 = mbox_max_channels_get_dt(&rx_channel_incorrect);
+	TC_PRINT("mbox_max_channels_get_dt(rx_channel_incorrect): %d\n", ret2);
+	zassert_true(
+		(ret2 > 0),
+		"mbox_max_channels_get_dt(rx_channel_incorrect) shall return value greater than 0"
+		" got unexpected %d",
+		ret2
+	);
+
+	zassert_true(
+		(ret1 == ret2),
+		"mbox_max_channels_get_dt() shall return same value disregarding channel No."
+		" got unexpected %d and %d",
+		ret1,
+		ret2
+	);
+}
+
+static void *suite_setup(void)
+{
+	TC_PRINT("Test executed on %s\n", CONFIG_BOARD_TARGET);
+	TC_PRINT("===================================================================\n");
+
+	return NULL;
+}
+
+ZTEST_SUITE(mbox_error_cases, NULL, suite_setup, NULL, NULL, NULL);